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11.
Prof. Li Chen Genevieve E. Mullen Myriam Le Roch Cody G. Cassity Prof. Nicolas Gouault Prof. Henry Y. Fadamiro Prof. Robert E. Barletta Prof. Richard A. O'Brien Prof. Richard E. Sykora Prof. Alexandra C. Stenson Prof. Kevin N. West Howard E. Horne Jeffrey M. Hendrich Kang Rui Xiang Prof. James H. Davis Jr. 《Angewandte Chemie (International ed. in English)》2014,53(44):11762-11765
The practical utility of ionic liquids (ILs) makes the absence (heretofore) of reported examples from nature quite puzzling, given the facility with which nature produces many other types of exotic but utilitarian substances. In that vein, we report here the identification and characterization of a naturally occurring protic IL. It can be formed during confrontations between the ants S. invicta and N. fulva. After being sprayed with alkaloid‐based S. invicta venom, N. fulva detoxifies by grooming with its own venom, formic acid. The mixture is a viscous liquid manifestly different from either of the constituents. Further, we find that the change results as a consequence of formic acid protonation of the N centers of the S. invicta venom alkaloids. The resulting mixed‐cation ammonium formate milieu has properties consistent with its classification as a protic IL. 相似文献
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Femtosecond Laser-Induced Breakdown Spectroscopy for Detection of Trace Elements in Sophora Leaves 总被引:1,自引:0,他引:1 下载免费PDF全文
Sophora leaves from several areas in Beijing are analysed by femtosecond laser-induced breakdown spectroscopy (femto-LIBS). Although the used spectral detection system is not time-resolved, the spectral lines of trace mineral elements are detected and analysed. It is proven that the femto-LIBS can be an efficient method to detect mineral trace elements contained in tree leaves which is a biomonitor for atmospheric pollution assessment or botanic studies. An interesting case of correlation between trace elements detected in tree leaves and the pollution of the concerned area is presented, for the first time to our knowledge. 相似文献
14.
Alessandro Bencini Myriam G. Uytterhoeven Claudia Zanchini 《International journal of quantum chemistry》1994,52(4):903-918
Spin-polarized Xα–SW calculations of [Fe6(μ3?S)8(PH3)6]2+ as a model of the cluster [Fe6(μ3?S)8(PEt3)6] (BPh4)2 have been performed. The highest occupied energy levels are well separated from empty levels, and up to a maximum of eight electrons can be unpaired, giving a maximum spin state with S = 4. This electronic state is consistent with the magnetic data of [Fe6(μ3?S)8(PEt3)6](BPh 4)2, which have been interpreted using the Heisenberg–Dirac–Van Vleck exchange spin Hamiltonian. The S = 4 state arises from the magnetic coupling between five low-spin (Si = 1/2) and one intermediate-spin (S = 3/2) iron(III) center. © 1994 John Wiley & Sons, Inc. 相似文献
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The potential of a series of newly synthesized poly(N,N-dimethylacrylamide) (PDMA) grafted polyacrylamide (PAM) copolymers (P(AM-PDMA)) as a replaceable separation medium for protein analysis was studied. A comparative study with and without copolymers was performed; the separation efficiency, analysis reproducibility and protein recovery proved that the P(AM-PDMA) copolymers were efficient in suppressing the adsorption of basic proteins onto the silica capillary wall. Furthermore, the size-dependent retardation of native proteins in a representative P(AM-PDMA) copolymer was demonstrated by Ferguson analysis. The results showed that the P(AM-PDMA) copolymers combine the good coating property of PDMA and the sieving property of PAM and could be applied as a sieving matrix for the analysis of native proteins. 相似文献
17.
Gottfried Heinisch Barbara Matuszczak Elisabeth Spielmann Myriam Witvrouw Christophe Pannecouque Erik De Clercq 《Journal of heterocyclic chemistry》2001,38(1):125-130
Two methods for the preparation of dialkylsubstituted dipyridazino[4,3‐b:3′,4′‐e][1,4]diazepinones and dipyridazino[3,4‐b:3′,4′‐e][1,4]diazepinones are reported. The new compounds were evaluated for their inhibitory effects against the replication of human immunodeficiency virus [HIV‐1(IIIB) and HIV‐2(ROD)] in MT‐4 cells. 相似文献
18.
Matthieu Baudelet Myriam Boueri Jin Yu Samuel S. Mao Vincent Piscitelli Xianglei Mao Richard E. Russo 《Spectrochimica Acta Part B: Atomic Spectroscopy》2007,62(12):1329-1334
Ultraviolet pulses (266 nm) delivered by a quadrupled Nd:YAG laser were used to analyze organic samples with laser-induced breakdown spectroscopy (LIBS). We present characteristics of the spectra obtained from organic samples with special attentions on the emissions of organic elements, O and N, and molecular bonds CN. The choice of these atomic or molecular species is justified on one hand, by the importance of these species to specify organic or biological materials; and on the other hand by the possible interferences with ambient air when laser ablation takes place in the atmosphere. Time-resolved LIBS was used to determine the time-evolution of line intensity emitted from these species. We demonstrate different kinetic behaviors corresponding to different origins of emitters: native atomic or molecular species directly vaporized from the sample or those generated through dissociation or recombination due to interaction between laser-induced plasma and air molecules. Our results show the ability of time-resolved UV-LIBS for detection and identification of native atomic or molecular species from an organic sample. 相似文献
19.
This study is directed towards investigating the role of the surface treatment of clay particles on the rheological and thermomechanical
behaviour of clay-epoxy blends. Nanocomposites were prepared by mixing small amounts (5–10 mass %) of commercial organoclays
or raw clays with an epoxy system commonly used in civil engineering. Rheological characterisations in the liquid state revealed
a pronounced thixotropic character of the organoclay-based systems, which all exhibited a shear-thinning behaviour above a
critical stress threshold (yield stress), depending on both the intensity of interfacial interactions and the degree of filler
dispersion. On the other hand, systems based on raw clay particles behaved like Newtonian fluids, in the same way as the unreinforced
polymer matrix. Complementary dynamic mechanical analyses (DMA) performed on the cured cross-linked nanocomposites also showed
significant changes in the viscoelastic behaviour of the epoxy matrix due to the introduction of organoclays, whereas only
minor variations were observed following the introduction of raw fillers. These results were consistent with nanoscale morphological
characterisations performed by conventional X-ray diffraction (XRD) on the various hybrid systems. In this context, rheology
and DMA appear as attractive alternative methods for assessing the filler dispersion at a macroscopic (and possibly more relevant)
scale. This research is of practical interest for civil engineers, since clay reinforced-epoxies could in the future be used
as coating materials with enhanced barrier performances, in order to protect infrastructures against environmental ageing
or corrosion. 相似文献
20.
For integers m, k≥1, we investigate the maximum size of a directed cut in directed graphs in which there are m edges and each vertex has either indegree at most k or outdegree at most k. © 2009 Wiley Periodicals, Inc. J Graph Theory 相似文献