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91.
92.
Candice Botuha Fabrice Chemla Franck Ferreira Julien Louvel Alejandro Pérez-Luna 《Tetrahedron: Asymmetry》2010,21(9-10):1147-1153
The stereoselective synthesis of alkynyl 1,2-amino alcohols by the addition of 3-chloro- and 3-methoxymethoxy- allenylzincs to chiral tert-butylsulfinylimines is described. The methodology is applicable to the preparation of alkynyl 2-amino-1,3-diols (O,N,O stereotriads) using α-alkoxy tert-butylsulfinylimines as chiral starting materials. The scope and limitations of the methodology along with recent applications to the efficient asymmetric syntheses of natural and/or bioactive alkaloids and polyhydroxylated alkaloids are presented. 相似文献
93.
94.
Franck Pastor Malorie Trillat Joseph Pastor Etienne Loute 《Comptes Rendus Mecanique》2006,334(4):213-219
A nonlinear interior point method associated with the kinematic theorem of limit analysis is proposed. Associating these two tools enables one to determine an upper bound of the limit loading of a Gurson material structure from the knowledge of the sole yield criterion. We present the main features of the interior point algorithm and an original method providing a rigorous kinematic bound from a stress formulation of the problem. This method is tested by solving in plane strain the problem of a Gurson infinite bar compressed between rough rigid plates. To cite this article: F. Pastor et al., C. R. Mecanique 334 (2006). 相似文献
95.
In this Note we describe a preconditionner for iteratively solving the linear system arising from the discretization of a general nonseparable elliptic problem by spectral element method. This preconditionner is constructed from approximating the original problem with the closest (in some sense) separable elliptic problem. A direct method is then used to invert the preconditionner. To cite this article: M. Azaïez et al., C. R. Mecanique 331 (2003). 相似文献
96.
Bilé EG Sassine R Denicourt-Nowicki A Launay F Roucoux A 《Dalton transactions (Cambridge, England : 2003)》2011,40(24):6524-6531
Novel anionic species, such as hydrogen carbonate (HCO(3)(?)), fluoride (F(?)), triflate (CF(3)SO(3)(?)), tetrafluoroborate (BF(4)(?)) and chloride (Cl(?)) were investigated as new partners of water soluble N,N-dimethyl-N-cetyl-N-(2-hydroxyethyl) ammonium salts, used as a protective agent of rhodium colloids. The effect of the surfactant polar head on the micellar behavior, size and morphology of the nanospecies was studied by adapted physico-chemical experiments (surface tension measurements, dynamic light scattering, thermogravimetric and TEM analyses) and discussed in terms of strong or weak stabilization of the growing nanoparticles surface. Finally, the influence of the nanoenvironment generated by the surfactant with various counter-anions was evaluated via the hydrogenation of aromatics. 相似文献
97.
Bonnel D Longuespee R Franck J Roudbaraki M Gosset P Day R Salzet M Fournier I 《Analytical and bioanalytical chemistry》2011,401(1):149-165
The large amount of data generated using matrix-assisted laser desorption/ionization mass spectrometric imaging (MALDI-MSI)
poses a challenge for data analysis. In fact, generally about 1.108–1.109 values (m/z, I) are stored after a single MALDI-MSI experiment. This imposes processing techniques using dedicated informatics tools
to be used since manual data interpretation is excluded. This work proposes and summarizes an approach that utilizes a multivariable
analysis of MSI data. The multivariate analysis, such as principal component analysis–symbolic discriminant analysis, can
remove and highlight specific m/z from the spectra in a specific region of interest. This approach facilitates data processing and provides better reproducibility,
and thus, broadband acquisition for MALDI-MSI should be considered an effective tool to highlight biomarkers of interest.
Additionally, we demonstrate the importance of the hierarchical classification of biomarkers by analyzing studies of clusters
obtained either from digested or undigested tissues and using bottom-up and in-source decay strategies for in-tissue protein
identification. This provides the possibility for the rapid identification of specific markers from different histological
samples and their direct localization in tissues. We present an example from a prostate cancer study using formalin-fixed
paraffin-embedded tissue. 相似文献
98.
Martineau C Fayon F Suchomel MR Allix M Massiot D Taulelle F 《Inorganic chemistry》2011,50(6):2644-2653
The room temperature structure of Ba(5)Al(3)F(19) has been solved using electron microscopy and synchrotron powder diffraction data. One-dimensional (1D) (27)Al and ultrafast magic-angle-spinning (MAS) (19)F NMR spectra have been recorded and are in agreement with the proposed structural model for Ba(5)Al(3)F(19). The (19)F isotropic chemical shift and (27)Al quadrupolar parameters have been calculated using the CASTEP code from the experimental and density functional theory geometry-optimized structures. After optimization, the calculated NMR parameters of both the (19)F and (27)Al nuclei show improved consistency with the experimental values, demonstrating that the geometry optimization step is necessary to obtain more accurate and reliable structural data. This also enables a complete and unambiguous assignment of the (19)F MAS NMR spectrum of Ba(5)Al(3)F(19). Variable-temperature 1D MAS (19)F NMR experiments have been carried out, showing the occurrence of fluorine ion mobility. Complementary insights were obtained from both two-dimensional (2D) exchange and 2D double-quantum dipolar recoupling NMR experiments, and a detailed analysis of the anionic motion in Ba(5)Al(3)F(19) is proposed, including the distinction between reorientational processes and chemical exchange involving bond breaking and re-formation. 相似文献
99.
100.
Toufik Kanit Samuel ForestDominique Jeulin Franck N’GuyenScott Singleton 《Mechanics Research Communications》2011,38(2):136-140
Optimal shape design of microstructured materials has recently attracted a great deal of attention in materials science. The shape and the topology of the microstructure have a significant impact on the macroscopic properties. This paper presents different computational models of random microstructures, to virtually improve the physical properties of ice cream. Several sensory properties of this heterogeneous material issued from food industry are directly controlled by the elastic and thermal conducting ones. The material effective elastic and thermal conducting properties are obtained through direct large scale numerical simulations. The different formulations address the problem of finding the shape of the representative microstructural element for random heterogeneous media that increase the elastic moduli and thermal conductivity compared to existing products. The computational models are established using finite element method and images of virtual microstructures. In this paper we propose a new model of microstructures. This model is constructed with hexagonal prismatic rods and plates with volume fractions around 0.7 for the hard phase represented by hexagons of ice. A comparison between three two-phase elastic heterogeneous microstructures models is drawn. This illustrates the concept of design of microstructures using computational homogenization tools. 相似文献