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101.
Seindé Touré Isabelle Dusfour Didier Stien Véronique Eparvier 《Tetrahedron letters》2017,58(38):3727-3729
Two new tetrahydrofuran derivatives, mucorinic acids A (1) and B (2) as well as the three known secondary metabolites dehydroabietic acid (3), Δ8-dihydroabietic acid (4) and 8-pimarenic acid (5) were isolated from a solid culture of the fungus Mucor spp. isolated on insect Acalymma bivittula. The structure of these compounds was elucidated by analysis of NMR and MS spectroscopic data. Compounds were tested in antimicrobial and insecticidal assays. Dehydroabietic acid exhibited moderate larvicidal activity on Aedes aegypti larvae with 65% mortality at 10 ppm. Both new compounds 1 and 2 showed interesting antibacterial activity on Staphylococcus aureus and methicillin resistant S. aureus with MIC values in the 8–16 μg/ml. 相似文献
102.
Bryan S. Holtzman Eric T. Roberts Nicholas S. Caminiti Jacob A. Fox Madison B. Goodstein Staci A. Hill Zitong B. Jia Isabelle N.-M. Leibler Michael L. Martini Gina M. Mendolia Sarah B. Nodder Molly S. Costanza-Robinson Richard C. Bunt 《Tetrahedron letters》2017,58(5):432-436
A nucleophile crossover experiment was used to monitor the reversibility of nucleophilic addition of benzylamine to π-allylpalladium complexes. Dppe, dppp, dppb, and PHOX showed more crossover than PPh3 and dppm in both DMF and dichloromethane. Crossover was inhibited by the addition of DBU or Cs2CO3, but much less elimination to diene side products was observed with Cs2CO3. Analysis of percent crossover vs. percent reaction completion using the PHOX ligand revealed that with added DBU or Cs2CO3 crossover only began occurring after 100% completion had been reached. 相似文献
103.
Sharma SK Roudaut G Fabing I Duplâtre G 《Physical chemistry chemical physics : PCCP》2010,12(42):14278-14284
The triplet state of positronium, o-Ps, is used as a probe to characterize a starch-20% w/w sucrose matrix as a function of temperature (T). A two-step decomposition (of sucrose, and then starch) starts at 440 K as shown by a decrease in the o-Ps intensity (I(3)) and lifetime (τ(3)), the latter also disclosing the occurrence of a glass transition. Upon sucrose decomposition, the matrix acquires properties (reduced size and density of nanoholes) that are different from those of pure starch. A model is successfully established, describing the variations of both I(3) and τ(3) with T and yields a glass transition temperature, T(g) = (446 ± 2) K, in spite of the concomitant sucrose decomposition. Unexpectedly, the starch volume fraction (as probed through thermal gravimetry) decreases with T at a higher rate than the free volume fraction (as probed through PALS). 相似文献
104.
The ground state, oxidized ground state, (3)MLCT and (3)MC excited states have been studied by DFT and TDDFT for two Ru(II) complexes bearing an N(6) or N(5)C coordination sphere. The effect of replacing one Ru-N dative bond by one Ru-C covalent bond have been studied and quantified on their ground state by the means of geometry optimization, NBO analysis and calculation of their IR vibrations. IR fingerprints of the Ru-C bond have been found at 945 and 1113 cm(-1). In addition, this study confirmed and quantified the effects of N→C(-) substitution on the spectroscopic properties of the [RuN(5)C](+) complex: a broader and bathochromically-shifted absorption spectrum, a smaller ground-(3)MLCT energy gap and a highly energetic (3)MC state are the major characteristics of the carbon-containing monocationic complex. 相似文献
105.
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
106.
Gaëlle Semard Valerie Peulon-Agasse Auguste Bruchet Jean-Philippe Bouillon Pascal Cardinaël 《Journal of chromatography. A》2010,1217(33):5449-5454
It is important to develop methods of optimizing the selection of column sets and operating conditions for comprehensive two-dimensional gas chromatography. A new method for the calculation of the percentage of separation space used was developed using Delaunay's triangulation algorithms (convex hull). This approach was compared with an existing method and showed better precision and accuracy. It was successfully applied to the selection of the most convenient column set and the geometrical parameters of second column for the analysis of 49 target compounds in wastewater. 相似文献
107.
108.
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
109.
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
110.
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