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51.
The results of a mass spectrometric analysis of the series C6Cl6; C6Cl5F; 1,3-F2C6Cl4; 1,3,5-F3C6Cl3; 1,2,3,5-F4C6Cl2; C6F5Cl; C6F6 obtained by successive replacements of chlorine atoms by fluorine atoms, starting with hexachlorobenzene, are presented. Similarly the corresponding series of perfluorochloropyridines are examined. The sequences of degradation observed are quite regular in both series, and correspond to possible simple mechanisms often confirmed by the observations of the corresponding metastable ions. 相似文献
52.
Jean-Baptiste Baugros Cécile Cren-Olivé Barbara Giroud Jean-Yves Gauvrit Pierre Lantéri Marie-Florence Grenier-Loustalot 《Journal of chromatography. A》2009,1216(25):4941-4949
The study proposes an analytical method to quantify 10 alkylphenols and 12 pesticides at ultra-trace levels by liquid chromatography in reverse mode coupled to positive electrospray ionisation–tandem mass spectrometry. The extraction procedure from environmental solids was optimised by pressurised liquid extraction using acetonitrile:isopropanol (1:1, v/v). The influence of several extraction experimental factors, temperature, pressure, duration and number of cycles, related to the PLE was investigated by an original and efficient chemometric approach. The optimised extraction method (80 °C, 40 bar, 10 min, 1 cycle) exhibited recoveries between 67 and 127% with RSD mostly under 13%. The whole method was applied to real samples: sludge, suspended materials, atmospheric fallouts and roof deposit. Pollutant levels were between 1 μg kg−1 and 5.9 mg kg−1. 相似文献
53.
Kpotin Gaston A. Bédé Affoué Lucie Houngue-Kpota Alice Anatovi Wilfried Kuevi Urbain A. Atohoun Guy S. Mensah Jean-Baptiste Gómez-Jeria Juan S. Badawi Michael 《Structural chemistry》2019,30(6):2301-2310
Structural Chemistry - Malaria is an important disease causing many death in several countries of Africa and Asia. In these continents, some plants such as Garcinia cola are used to fight against... 相似文献
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56.
In this note, we construct a 2-basic set of the alternating group
\mathfrakAn{\mathfrak{A}_n}. To do this, we construct a 2-basic set of the symmetric group
\mathfrakSn{\mathfrak{S}_n} with an additional property, such that its restriction to
\mathfrakAn{\mathfrak{A}_n} is a 2-basic set. We adapt here a method developed by Brunat and Gramain (J. Reine Angew. Math., to appear) for the case
when the characteristic is odd. One of the main tools is the generalized perfect isometries defined by Külshammer et al. (Invent.
Math. 151, 513–552, (2003)). 相似文献
57.
Conditions for Global Optimality 2 总被引:5,自引:0,他引:5
Jean-Baptiste Hiriart-Urruty 《Journal of Global Optimization》1998,13(4):349-367
In this paper bearing the same title as our earlier survey-paper [11] we pursue the goal of characterizing the global solutions of an optimization problem, i.e. getting at necessary and sufficient conditions for a feasible point to be a global minimizer (or maximizer) of the objective function. We emphasize nonconvex optimization problems presenting some specific structures like convex-anticonvex ones or quadratic ones. 相似文献
58.
We have synthesised all the fluorinated derivatives of perchloropyrimidine, trichloro-2,4,6-pyrimidine and perchloro-s-triazine. Fluorine n.m.r. analysis, associated with gas chromatography coupled with mass spectrometry, allowed separation and identification of the products. The behaviour of these compounds under electron-impact is presented and discussed here. 相似文献
59.
Complex calculators in the classroom: theoretical and practical reflections on teaching pre-calculus
Jean-Baptiste Lagrange 《International Journal of Computers for Mathematical Learning》1999,4(1):51-81
University and older school students following scientific courses now use complex calculators with graphical, numerical and symbolic capabilities. In this context, the design of lessons for 11th grade pre-calculus students was a stimulating challenge.In the design of lessons, emphasising the role of mediation of calculators and the development of schemes of use in an 'instrumental genesis' was productive. Techniques, often discarded in teaching with technology, were viewed as a means to connect task to theories. Teaching techniques of use of a complex calculator in relation with 'traditional' techniques was considered to help students to develop instrumental and paper/pencil schemes, rich in mathematical meanings and to give sense to symbolic calculations as well as graphical and numerical approaches.The paper looks at tasks and techniques to help students to develop an appropriate instrumental genesis for algebra and functions, and to prepare for calculus. It then focuses on the potential of the calculator for connecting enactive representations and theoretical calculus. Finally, it looks at strategies to help students to experiment with symbolic concepts in calculus.This revised version was published online in September 2005 with corrections to the Cover Date. 相似文献
60.
We identify a class of composite membranes: fluid bilayers coupled to an elastic meshwork that are such that the meshwork's energy is a function F(el)[A(xi)] not of the real microscopic membrane area A, but of a smoothed membrane's area A(xi), which corresponds to the area of the membrane coarse grained at the mesh size xi. We show that the meshwork modifies the membrane tension sigma both below and above the scale xi, inducing a steep crossover of amplitude deltasigma=dF(el)/dA(xi). The predictions of our model account for the fluctuation spectrum of red blood cell membranes coupled to their cytoskeleton. Our results indicate that the cytoskeleton might be under extensional stress, which would provide a means to regulate available membrane areas. We also predict an observable tension jump for membranes decorated with polymer "brushes." 相似文献