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排序方式: 共有174条查询结果,搜索用时 15 毫秒
1.
Unexpected benzimidazole ring formation from a quinoneimide species in the presence of ammonium acetate as supporting electrolyte used in the coupling of electrochemistry with mass spectrometry 下载免费PDF全文
2.
Steffen Dachwitz Bjarne Scharkowski Prof. Norbert Sewald 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(72):18043-18046
Mild transition-metal catalysed cross-couplings enable direct functionalisation of biocatalytically halogenated tryptophans with alkyl iodides, representing a new alternative for late-stage derivatisations of halogenated aromatic amino acids. Moreover, this strategy enables preparation of (homo)tryptophan regioisomers in a simple two-step synthesis using a Pd-catalysed Negishi cross coupling. This method provides access to non-canonical constitutional surrogates of tryptophan, ready for use in peptide synthesis. 相似文献
3.
It is demonstrated that multiple 1D Raman scattering, Rayleigh scattering, and laser-induced fluorescence (LIF) measurements
can be performed simultaneously. This can be used for quasi-2D (or quasi-3D) single-shot measurements of multiple species
and the temperature in turbulent reacting and non-reacting flows. The technique has the potential to yield more precise information
than most competitive planar imaging approaches in combustion. For example, it can be used to overcome Raman/LIF interference
problems in technical flames. This is achieved by a new optical set-up that makes use of an imaging spectrograph combined
with fiber optics.
Received: 13 October 1999 / Revised version: 26 November 1999 / Published online: 27 January 2000 相似文献
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6.
Andreia F. Sousa Alessandro Gandini Armando J. D. Silvestre Carlos Pascoal Neto José J. C. Cruz Pinto Christer Eckerman Bjarne Holmbom 《Journal of polymer science. Part A, Polymer chemistry》2011,49(10):2281-2291
This article reports the successful synthesis and characterization of two types of completely biobased polymers prepared by the polycondensation or polytransesterification of suberin fragments, isolated by different procedures and from two different vegetable sources. These polymerizations were conducted with different experimental conditions in terms of the type of catalyst, the reaction medium and temperature, as well as the molar ratio between the reactive moieties. The ensuing linear or partly crosslinked polyesters were characterized by conventional spectroscopic techniques, SEC, DSC, XRD, DMA, and TGA. These hydrophobic materials represent an original contribution to the growing field of polymers from renewable resources. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
7.
Sten Scheibye Bjarne S. Pedersen S.-O. Lawesson 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-2):271-272
Abstract Recent studies have shown that the dimer of p-methoxyphenylthionophosphinesulfide, 1, is a very superior thiation reagent, as ketones, amides, and esters are in most cases quantitatively converted to their thio-analogues. 相似文献
8.
AH Pham B Lundgren B Stage M Møller Pedersen M Bachmann Nielsen MC Hemmsen J Arendt Jensen 《The Journal of the Acoustical Society of America》2012,132(1):487-497
Simulation of ultrasound images based on computed tomography (CT) data has previously been performed with different approaches. Shadow effects are normally pronounced in ultrasound images, so they should be included in the simulation. In this study, a method to capture the shadow effects has been developed, which makes the simulated ultrasound images appear more realistic. The method using a focused beam tracing model gives diffuse shadows that are similar to the ones observed in measurements on real objects. Ultrasound images of a cod (Gadus morhua) were obtained with a BK Medical 2202 ProFocus ultrasound scanner (BK Medical, Herlev, Denmark) equipped with a dedicated research interface giving access to beamformed radio frequency data. CT images were obtained with an Aquilion ONE Toshiba CT scanner (Toshiba Medical Systems Corp., Tochigi, Japan). CT data were mapped from Hounsfield units to backscatter strength, attenuation coefficients, and characteristic acoustic impedance. The focused beam tracing model was used to create maps of the transmission coefficient and scattering strength maps. Field II was then used to simulate an ultrasound image of 38.9 × 55.3 × 4.5 mm, using 10(6) point scatterers. As there is no quantitative method to assess quality of a simulated ultrasound image compared to a measured one, visual inspection was used for evaluation. 相似文献
9.
Simulated annealing and genetic algorithms for minimizing mean flow time in an open shop 总被引:1,自引:0,他引:1
Michael Andresen Heidemarie Brsel Marc Mrig Jan Tusch Frank Werner Per Willenius 《Mathematical and Computer Modelling》2008,48(7-8):1279-1293
This paper considers the problem of scheduling n jobs on m machines in an open shop environment so that the sum of completion times or mean flow time becomes minimal. It continues recent work by Bräsel et al. [H. Bräsel, A. Herms, M. Mörig, T. Tautenhahn, T. Tusch, F. Werner, Heuristic constructive algorithms for open shop scheduling to minmize mean flow time, European J. Oper. Res., in press (doi.10.1016/j.ejor.2007.02.057)] on constructive algorithms. For this strongly NP-hard problem, we present two iterative algorithms, namely a simulated annealing and a genetic algorithm. For the simulated annealing algorithm, several neighborhoods are suggested and tested together with the control parameters of the algorithm. For the genetic algorithm, new genetic operators are suggested based on the representation of a solution by the rank matrix describing the job and machine orders. Extensive computational results are presented for problems with up to 50 jobs and 50 machines, respectively. The algorithms are compared relative to each other, and the quality of the results is also estimated partially by a lower bound for the corresponding preemptive open shop problem. For most of the problems, the genetic algorithm is superior when fixing the same number of 30 000 generated solutions for each algorithm. However, in contrast to makespan minimization problems, where the focus is on problems with an equal number of jobs and machines, it turns out that problems with a larger number of jobs than machines are the hardest problems. 相似文献
10.
The rotational spectrum of 2-methylpyridine (α-picoline, CH3C5H4N) in the two lowest levels of methyl internal rotation (m=0, ±1) has been recorded in the frequency range from 2 to 15 GHz using a molecular beam Fourier transform microwave spectrometer. The high resolution and sensitivity of this spectroscopic technique allowed resolution of hyperfine structures due to l4N nuclear quadrupole coupling with high accuracy and detection of the spectra of the 15N- and all 13C-isotopomers. These investigations considerably extend the results from an earlier study on the normal species (Dreizler, H., Rudolph, H. D., and Mader, H., 1970, Z. Naturforsch., 25a, 25); improved rotational and centrifugal distortion constants as well as all components of the 14N quadrupole coupling tensor have been obtained. Analysis of the spectra of the isotopomers yielded the I4N quadrupole coupling constants χ cc and χ aa – χ bb (for the 13C species), the potential parameter V 3 for the barrier hindering the internal rotation of the methyl group, and, in particular, ro, rs r m (1) and r m (2) structural parameters for the molecule. In addition to the microwave studies on the monomer, we have also investigated the rotational spectrum of the weakly bound dimer of normal 2-methylpyridine with Ar. The results obtained for the quadrupole coupling constants and the hindering potential for the internal methyl rotation show that the corresponding parameters are not significantly, or only slightly, changed in the complex. 相似文献