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101.
Allegrand J Touboul D Schmitz-Afonso I Guérineau V Giuliani A Le Ven J Champy P Laprévote O 《Rapid communications in mass spectrometry : RCM》2010,24(24):3602-3608
Collision‐induced dissociation experiments of seven annonaceous acetogenins were carried out under high and low collision energy conditions. Each compound was studied as protonated or deprotonated and lithium‐ or sodium‐ cationized molecules, using ElectroSpray Ionisation (ESI) with a hybrid linear trap/orbitrap mass spectrometer (LTQ‐Orbitrap®). The same ion species were studied with a Matrix‐Assisted Laser Desorption Ionisation (MALDI) tandem mass spectrometer in a high collision energy regime (1 or 2 keV). Although each of the techniques showed some limitations in the detection of functional groups, unambiguous structural identification of the acetogenins was obtained. MALDI ToF‐ToF has the advantage over ESI‐based methods to provide mass spectra rich in informative fragments which allows the confirmation of some functional groups position. By contrast, ESI‐LTQ‐Orbitrap® analysis has the advantage over MALDI that the mass spectra are relatively simple with only fragments close to the functional groups. However, this technique needs to carry out experiments both in negative and positive ionization modes. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
102.
103.
Noirot IC Brittan-Powell EF Dooling RJ 《The Journal of the Acoustical Society of America》2011,129(6):3445-3448
Auditory brainstem responses (ABRs) were recorded in adult budgerigars, canaries, and zebra finches in quiet and in three levels of white noise for tone stimuli between 1 and 4 kHz. Similar to behavioral results, masked ABR thresholds increased linearly with increasing noise levels. When the three species are considered together, ABR-derived CRs were higher than behavioral CRs by 18-23 dB between 2 and 4 kHz and by about 30 dB at 1 kHz. This study clarifies the utility of using ABRs for estimating masked auditory thresholds in natural environmental noises in species that cannot be tested behaviorally. 相似文献
104.
Antoni T Kuhn AG Briant T Cohadon PF Heidmann A Braive R Beveratos A Abram I Le Gratiet L Sagnes I Robert-Philip I 《Optics letters》2011,36(17):3434-3436
We have designed photonic crystal suspended membranes with optimized optical and mechanical properties for cavity optomechanics. Such resonators sustain vibration modes in the megahertz range with quality factors of a few thousand. Thanks to a two-dimensional square lattice of holes, their reflectivity at normal incidence at 1064?nm reaches values as high as 95%. These two features, combined with the very low mass of the membrane, open the way to the use of such periodic structures as deformable end mirrors in Fabry-Perot cavities for the investigation of cavity optomechanical effects. 相似文献
105.
Isabelle Piot-Lepetit Rozenn Perrigot Gérard Cliquet 《The Journal of the Operational Research Society》2014,65(11):1692-1699
A meta-DEA (Data Envelopment Analysis) approach is used to analyse the impact of the industry in which the franchisor operates its business on its chain efficiency by comparing chain efficiency between and across industries (retail versus services). To provide realistic short-term and long-term objectives to inefficient chains, a level-by-level benchmarking path is developed with the context-dependent DEA approach. Furthermore, the joint implementation of both approaches enables an identification of chains for which the industry influences their efficiency, an evaluation of the efficiency share that results from industry-specific factors rather than factors common to the franchise sector as a whole, and the characterization of an implementable and achievable benchmarking defining level-by-level improvements of chain efficiency and taking into account chain characteristics. Such an analysis can help franchisors to define their future strategic and managerial orientations. 相似文献
106.
This paper shows that the boundedness of a weighted composition operator on the Hardy–Hilbert space on the disc or half-plane implies its boundedness on a class of related spaces, including weighted Bergman spaces. The methods used involve the study of lower-triangular and causal operators. 相似文献
107.
Isabelle Minet Laszlo Hevesi Manuel Azenha Joseph Delhalle Zineb Mekhalif 《Journal of chromatography. A》2010,1217(17):2758-2767
We report on the fabrication and performances of a solid-phase microextraction (SPME) fiber based on a stainless steel wire coated with a covalently attached polyacrylonitrile (PAN)/multi-walled carbon nanotubes (MWCNTs) composite. This new coating is obtained by atom transfer radical polymerization (ATRP) of acrylonitrile mixed with MWCNTs. ATRP is initiated from 11-(2-bromo-2-methylpropionyloxy)-undecyl-phosphonic acid molecules grafted on the wire surface via the phosphonic acid group. The extraction performances of the fibers are assessed on different classes of compounds (polar, non-polar, aromatic, etc.) from water solutions by headspace extraction. The optimization of the parameters affecting the extraction efficiency of the target compounds was studied as well as the reproducibility and the repeatability of the fiber. The fibers sustain more than 200 extractions during which they remain chemically stable and maintain good performances (detection limits lower than 2 μg/l, repeatability, etc.). Considering their robustness together with their easy and inexpensive fabrication, these fibers could constitute promising alternatives to existing products. 相似文献
108.
Alexandre Lumbroso Isabelle Beaudet Thierry Besson Erwan Le Grognec 《Tetrahedron》2009,65(45):9180-45
An efficient and reproducible synthesis of various α-ethoxycarbamates is described via a microwave heating mode. Compared to the thermal process, the microwave dielectric heating induces a dramatic reduction of the reaction time and the improvement of the yields. The reaction is general since applicable to aromatic and aliphatic aldehydes with various primary amines. Several examples involving chiral aldehydes have also been considered. 相似文献
109.
Anna M. Maj Isabelle Suisse Catherine Méliet Francine Agbossou-Niedercorn 《Tetrahedron: Asymmetry》2010,21(16):2010-2014
The enantioselective hydrogenation of indole esters has been carried out efficiently in the presence of a rhodium catalyst modified by Walphos-type chiral ligands. The addition of a base can be beneficial in some catalytic conditions. 相似文献
110.