A multi-graph G on n vertices is (k,?)-sparse if every subset of n′?n vertices spans at most kn′-? edges. G is tight if, in addition, it has exactly kn-? edges. For integer values k and ?∈[0,2k), we characterize the (k,?)-sparse graphs via a family of simple, elegant and efficient algorithms called the (k,?)-pebble games. 相似文献
A new methodology for the preparation of carbohydrates locked in a 1,4B boat conformation is presented. The constrained molecules thus obtained are functionalized at the anomeric position by iodo-, fluoro-, hydroxyl- or/and phosphono-methylene moieties. A remarkable diastereoselective opening of these quaternary acetals was also observed under non-acidic conditions. 相似文献
Analytical and Bioanalytical Chemistry - A molecularly imprinted polymer (MIP) was designed in order to allow the selective solid-phase extraction of carbamazepine (CBZ), an anticonvulsant and... 相似文献
As evidenced by the number of publications and patents published in the last years, the radiosynthesis of 6-[18F]fluoro-3,4-dihydroxy-L-phenylalanine ([18F]FDOPA) using the nucleophilic [18F]F- process remains currently a challenge for the radiochemists scientific community even if promising methods for the radiofluorination of electron-rich aromatic structures were recently developed from arylboronate, arylstannane or iodonium salt precursors. In such context, based on the use of an iodonium triflate salt precursor, we optimized a fast and efficient radiofluorination route fully automated and free from any base, cryptand or metal catalyst for the radiosynthesis of [18F]FDOPA. Using this method, this clinically relevant radiotracer was produced in 64 min, 27–38 % RCY d.c. (n = 5), >99 % RCP, >99 % ee., and high Am 170–230 GBq/µmol. In addition, this optimization study clearly highlighted the important role of a triflate-hydrogen carbonate counterion exchange during the radiolabeling process to achieve high fluorine-18 incorporation yields. 相似文献
Summary: A quenched‐flow reactor is introduced as an effective means for the production of polyolefin particles with precisely controlled reaction times as low as 40 ms. The use of off‐line scanning electron microscopy and induced‐coupled plasma yields experimental data on the development of the kinetics and morphology of nascent structures during the polymerisation of ethylene on a heterogeneous TiCl4 MgCl2 Ziegler–Natta catalyst. Initial ex situ observations revealed the development of specific morphologies very early during the reaction (e.g., cracks in platelike surfaces, fines, extrudates, etc.) that can potentially lead to fines, and the kinetic analysis showed extremely high reaction rates at very short times.
Scanning electron micrograph of a network of fibrils formed by the deformation of the surface of a particle due to the generation of internal forces. 相似文献
An analytical methodology for quality control analyses of IgG and their impurities is presented using a new UV‐LIF (266 nm) detector inside the cassette of a CE instrument and its performance was evaluated. The observed sensitivity was very close to that obtained by silver staining of slab gels (LOD of 25 ng/mL), while the sensitivity of the analysis is 80 times better than with CE/UV absorption (214 nm). Examples of the analysis of pharmaceutical and other commercial IgGs are provided and the kinetics of the reduction of IgG by β‐mercaptoethanol is reported, demonstrating the ease of performing the analysis. 相似文献
[reaction: see text] A number of approaches for the synthesis of the 1H-indol-2-yl-1H-quinolin-2-one ring system found in the potent and selective KDR kinase inhibitor 1 are described. The preparation and reaction of trimethylsilylnitrobenzene 26 with 2-methoxy-3-quinolinecarboxaldehyde 28 afforded alcohol 30, which was the key intermediate for the preparation of the target compounds. Conversion of alcohol 30 to either nitroketone 36 or nitrostyrene 45 set the stage for reductive cyclization and the formation of indole 25. The quinolin-2-one functionality was unmasked in the last step to provide compound 1 in 56-60% overall yield from readily available starting materials. 相似文献
