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1.
A preparative route to cis- and trans-1,2-dibromocyclopropane () was developed via the Hunsdiecker reaction of silver cyclopropane-1,2-dicarboxylate (). Cis- and trans- gave the same ratio of cis- and trans- (1:3.2). The mechanism of this reaction is briefly discussed. 相似文献
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Maj-Britt Schmidt Andersen Mette Kristensen Claudine Manach Estelle Pujos-Guillot Sanne Kellebjerg Poulsen Thomas Meinert Larsen Arne Astrup Lars Dragsted 《Analytical and bioanalytical chemistry》2014,406(7):1829-1844
While metabolomics is increasingly used to investigate the food metabolome and identify new markers of food exposure, limited attention has been given to the validation of such markers. The main objectives of the present study were to (1) discover potential food exposure markers (PEMs) for a range of plant foods in a study setting with a mixed dietary background and (2) validate PEMs found in a previous meal study. Three-day weighed dietary records and 24-h urine samples were collected three times during a 6-month parallel intervention study from 107 subjects randomized to two distinct dietary patterns. An untargeted UPLC-qTOF-MS metabolomics analysis was performed on the urine samples, and all features detected underwent strict data analyses, including an iterative paired t test and sensitivity and specificity analyses for foods. A total of 22 unique PEMs were identified that covered 7 out of 40 investigated food groups (strawberry, cabbages, beetroot, walnut, citrus, green beans and chocolate). The PEMs reflected foods with a distinct composition rather than foods eaten more frequently or in larger amounts. We found that 23 % of the PEMs found in a previous meal study were also valid in the present intervention study. The study demonstrates that it is possible to discover and validate PEMs for several foods and food classes in an intervention study with a mixed dietary background, despite the large variability in such a dataset. Final validation of PEMs for intake of foods should be performed by quantitative analysis. Figure
Examples of two urinary exposure markers for cabbage (left) and beetroot (right) found in the study from an untargeted LC‐MS metabolomics analysis of urine samples and self‐reported food intake data 相似文献
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The complete system of fluid dynamics equations describing the development of instability of a reaction front in a two-dimensional
flow in reversed time are reduced to a closed system of equations of front dynamics by using Lagrangian variables and integrals
of motion. The system can be used to analyze processes behind the front without solving the complete system of fluid dynamics
and chemical kinetics equations. It is demonstrated how the gas density disturbances induced by the moving front can be described
in the adiabatic approximation. 相似文献
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In this paper we consider the Cumulative Capacitated Vehicle Routing Problem (CCVRP), which is a variation of the well-known Capacitated Vehicle Routing Problem (CVRP). In this problem, the traditional objective of minimizing total distance or time traveled by the vehicles is replaced by minimizing the sum of arrival times at the customers. We propose a branch-and-cut-and-price algorithm for obtaining optimal solutions to the problem. To the best of our knowledge, this is the first published exact algorithm for the CCVRP. We present computational results based on a set of standard CVRP benchmarks and investigate the effect of modifying the number of vehicles available. 相似文献
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V. B. Akkerman M. L. Zaytsev 《Computational Mathematics and Mathematical Physics》2011,51(8):1418-1430
A method for transforming the Euler and Navier-Stokes equations and a complete system of fluid dynamics equations in three
dimensions to a closed system on any moving surface is proposed. As a result, for an arbitrary geometric configuration, the
dimension of the equations is reduced by one, which makes them convenient for numerical simulation. The general principles
of the method are described, and verifying examples are presented. 相似文献