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961.
David Bouis Pascal Febvre 《Journal of Infrared, Millimeter and Terahertz Waves》2008,29(12):1156-1162
Sets of bow-tie antennas, used in a single emitter-receiver near-field configuration and in array configuration, have been studied to be used as wireless means to transmit 8–12 GHz microwave signals from the cold stage of a cryogenic system to a room-temperature processing unit. Indeed, the absence of heat conduction allows increasing the performance of cryogenic systems and open the way to multichannel microwave systems that are necessary for imagers. Transmission loss has been found to be lower than 3 dB over a 1.5 GHz bandwidth while crosstalk in the array configuration is kept below ?20 dB when antennas are located at around 90 mm transversally from each other. 相似文献
962.
Cesar Auguste Badji Jean Dorland Lynda Kheloul Dimitri Brard Pascal Richomme Abdellah Kellouche Claudio Roberto Azevedo de Souza Antnio Loureno Bezerra Sylvia Anton 《Molecules (Basel, Switzerland)》2021,26(15)
Essential oils of aromatic plants represent an alternative to classical pest control with synthetic chemicals. They are especially promising for the alternative control of stored product pest insects. Here, we tested behavioral and electrophysiological responses of the stored product pest Tribolium confusum, to the essential oil of a Brazilian indigenous plant, Varronia globosa, collected in the Caatinga ecosystem. We analyzed the essential oil by GC-MS, tested the effects of the entire oil and its major components on the behavior of individual beetles in a four-way olfactometer, and investigated responses to these stimuli in electroantennogram recordings (EAG). We could identify 25 constituents in the essential oil of V. globosa, with anethole, caryophyllene and spathulenole as main components. The oil and its main component anethole had repellent effects already at low doses, whereas caryophyllene had only a repellent effect at a high dose. In addition, the essential oil abolished the attractive effect of the T. confusum aggregation pheromone. EAG recordings revealed dose-dependent responses to the individual components and increasing responses to the blend and even more to the entire oil. Our study reveals the potential of anethole and the essential oil of V. globosa in the management of stored product pests. 相似文献
963.
Heuskin S Godin B Leroy P Capella Q Wathelet JP Verheggen F Haubruge E Lognay G 《Journal of chromatography. A》2009,1216(14):2768-2775
The chemical composition of Matricaria chamomilla L. and Nepeta cataria L. essential oils was determined by GC-MS on an apolar stationary phase by comparison of the characteristic fragmentation patterns with those of the Wiley 275L database. The GC-MS chromatograms were compared with those obtained by fast GC equipped with a direct resistively heated column (Ultra Fast Module 5% phenyl, 5 mx 0.1 mm, 0.1 microm film thickness). Analytical conditions were optimised to reach a good peak resolution (split ratio=1:100), with analysis time lower than 5 min versus 35-45 min required by conventional GC-MS. The fast chromatographic method was completely validated for the analysis of mono- and sesquiterpene compounds. Essential oils were then fractionated by column chromatography packed with silica gel. Three main fractions with high degree of purity in E-beta-farnesene were isolated from the oil of M. chamomilla. One fraction enriched in (Z,E)-nepetalactone and one enriched in beta-caryophyllene were obtained from the oil of N. cataria. These semiochemical compounds could act as attractants of aphid's predators and parasitoids. 相似文献
964.
965.
Christian Klemps Dipl.‐Chem. Elina Payet Lionel Magna Dr. Lucien Saussine Dr. Xavier F. Le Goff Dr. Pascal Le Floch Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(33):8259-8268
Chromium(III) complexes bearing R′N(CH2PR2)2 (PCNCP) ligands have been prepared. Upon activation with methylaluminoxane, these complexes proved to be effective in the selective tri‐ and tetramerization of ethylene. The formation of either 1‐hexene or 1‐octene was found to be highly dependent on the steric bulk of the substituents R on the phosphine moieties. This observation was rationalized by using density functional theory calculations on selected steps of the metallacyclic mechanism of the ethylene oligomerization reaction. 相似文献
966.
Pascal Lefèvre 《Integral Equations and Operator Theory》2009,63(4):557-569
We compute the essential norm of a composition operator relatively to the class of Dunford-Pettis operators or weakly compact
operators, on some uniform algebras of analytic functions. Even in the context of H∞ (resp. the disk algebra), this is new, as well for the polydisk algebras and the polyball algebras. This is a consequence
of a general study of weighted composition operators.
相似文献
967.
Thérèse Arliguie Pierre Thuéry Pascal Le Floch Nicolas Mézailles Michel Ephritikhine 《Polyhedron》2009
Treatment of UI3(THF)4 with [M(Et2O)][SPSMe] (M = Li, K; [SPSMe]− = 1-methyl-2,6-bis(diphenylphosphine sulfide)-3,5-diphenylphosphinine anion) gave the cationic tris SPS complex [U(SPSMe)3]I (1). Similar reaction of U(BH4)3(THF)3 and [M(Et2O)][SPSMe] afforded, in addition to the [U(SPS)3]+ cation, crystals of the sulfido complex [U{(μ3-S)4U3(SPSMe)3(BH4)3}2] (2). The metal environment in 1 is a tricapped trigonal prism and the core of the heptanuclear cluster 2 is a corner-shared double-cubane. 相似文献
968.
This paper addresses the question of producing modular sequential imperative code from synchronous data-flow networks. Precisely, given a system with several input and output flows, how to decompose it into a minimal number of classes executed atomically and statically scheduled without restricting possible feedback loops between input and output?Though this question has been identified by Raymond in the early years of Lustre, it has almost been left aside until the recent work of Lublinerman, Szegedy and Tripakis. The problem is proven to be intractable, in the sense that it belongs to the family of optimization problems where the corresponding decision problem—there exists a solution with size c—is NP-complete. Then, the authors derive an iterative algorithm looking for solutions for c=1,2,… where each step is encoded as a satisfiability (SAT) problem.Despite the apparent intractability of the problem, our experience is that real programs do not exhibit such a complexity. Based on earlier work by Raymond, the current paper presents a new encoding of the problem in terms of input/output relations. This encoding simplifies the problem, in the sense that it rejects some solutions, while keeping all the optimal ones. It allows, in polynomial time, (1) to identify nodes for which several schedules are feasible and thus are possible sources of combinatorial explosion; (2) to obtain solutions which in some cases are already optimal; (3) otherwise, to get a non trivial lower bound for c to start an iterative combinatorial search. The method has been validated on several industrial examples.The solution applies to a large class of block-diagram formalisms based on atomic computations and a delay operator, ranging from synchronous languages such as Lustre or Scade to modeling tools such as Simulink. 相似文献
969.
Thomas JH Grulier V Paillasseur S Pascal JC Le Roux JC 《The Journal of the Acoustical Society of America》2010,128(6):3554-3567
Near-field acoustic holography (NAH) is an effective tool for visualizing acoustic sources from pressure measurements made in the near-field of sources using a microphone array. The method involving the Fourier transform and some processing in the frequency-wavenumber domain is suitable for the study of stationary acoustic sources, providing an image of the spatial acoustic field for one frequency. When the behavior of acoustic sources fluctuates in time, NAH may not be used. Unlike time domain holography or transient method, the method proposed in the paper needs no transformation in the frequency domain or any assumption about local stationary properties. It is based on a time formulation of forward sound prediction or backward sound radiation in the time-wavenumber domain. The propagation is described by an analytic impulse response used to define a digital filter. The implementation of one filter in forward propagation and its inverse to recover the acoustic field on the source plane implies by simulations that real-time NAH is viable. Since a numerical filter is used rather than a Fourier transform of the time-signal, the emission on a point of the source may be rebuilt continuously and used for other post-processing applications. 相似文献
970.
Enhancement and quenching of single-molecule fluorescence 总被引:1,自引:0,他引:1
We present an experimental and theoretical study of the fluorescence rate of a single molecule as a function of its distance to a laser-irradiated gold nanoparticle. The local field enhancement leads to an increased excitation rate whereas nonradiative energy transfer to the particle leads to a decrease of the quantum yield (quenching). Because of these competing effects, previous experiments showed either fluorescence enhancement or fluorescence quenching. By varying the distance between molecule and particle we show the first experimental measurement demonstrating the continuous transition from fluorescence enhancement to fluorescence quenching. This transition cannot be explained by treating the particle as a polarizable sphere in the dipole approximation. 相似文献