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61.
Cristina Flox Javier Rubio-Garcia Raquel Nafria Reza Zamani Marcel Skoumal Teresa Andreu Jordi Arbiol Andreu Cabot Joan Ramon Morante 《Carbon》2012,50(6):2372-2374
Graphene-supported monometallic (Pt) and bimetallic (CuPt3) cubic nanocatalysts have been investigated as new positive electrode materials for improving the VO2+/VO2+ redox process occurring in the vanadium redox flow batteries (VRB). High-resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM) have been employed to characterize the electrodes. The presence of the CuPt3 nanocubes on graphene conferred higher electrocatalytic activity due to the much higher electroactive area compared to that obtained with the Pt nanoparticles. The electrochemical surface area of the nano-(CuPt3)-decorated graphene electrode was 105% higher compared to non-decorated graphene, being then a promising alternative for improving the VRB. 相似文献
62.
Synthesis and nuclear magnetic resonance properties of all geometrical isomers of conjugated linoleic acids 总被引:1,自引:0,他引:1
Pure geometric isomers of conjugated linoleic acid were prepared from castor oil as the primary starting material. Methyl
octadeca-9Z, 11E-dienoate (2) and methyl octadeca-9Z, 11Z-dienoate (4) were obtained by zinc reduction of methyl santalbate (1, methyl octadec-11E-en-9-ynoate) and methyl octadec-11 Z-en-9-ynoate (3), respectively, as the key intermediates. Methyl octadeca-9E, 11E-dienoate (8) and methyl octadeca-9E, 11Z-dienoate (9) were prepared by demesylation of the mesyloxy derivative of methyl ricinelaidate (6, methyl 12-hydroxy-octadec-9 E-enoate). A study of the nuclear magnetic resonance spectral properties was carried out and the shifts of the olefinic carbon
atoms of 18:2(9Z, 11E) (2) and 18:2(9E, 11Z) (9) were readily identified by a combination of incredible natural abundance double quantum transfer experiment, heteronuclear
multiple bond correlation, and 1H−13C correlation spectroscopy correlation techniques. Doubts remain in the absolute identification of the individual olefinic
carbon atoms of the 18:2(9Z, 11Z) (4) and 18:2(9E, 11E) (8), except the fact that the shifts of the “inner” (C-10 and C-11) and “outer” (C-9 and C-12) positioned olefinic carbon atoms
of the conjugated diene system are distinguishable. 相似文献
63.
Julia Perim de Faria Marcel Berg Andrew Freedman Timothy B. Onasch Andreas Petzold 《Aerosol science and technology》2017,51(11):1240-1253
An evaluation of the operation and performance of a Cavity Attenuated Phase-Shift Particle Extinction Monitor (CAPS PMex) was performed for use on board commercial aircraft as part of the research infrastructure IAGOS (In-service Aircraft for a Global Observing System, www.iagos.org). After extensive laboratory testing, a new flow system, using mass flow controllers, was installed to maintain constant purge and sample flows under low and varying pressure conditions. The instrument was then tested for pressures as low as 200 hPa and evaluated against particle-free compressed air and CO2. Extinction coefficients for the studied gases were in close agreement with literature values with differences between 2.2% and 8%, proving that the CAPS technology works at low pressures. The instrument's limit of detection, with respect to 3 times the variability of the background signal for the full pressure range, was 0.2 Mm?1 for 60s integration time. During its first research aircraft operations, the IAGOS instrument prototype, composed of one CAPS PMex and one OPC, showed excellent results regarding the stability of the instruments and the potential for characterizing different aerosol types and for estimating the contribution of sub- and super-μm sized particles to aerosol light extinction.Copyright © 2017 American Association for Aerosol Research 相似文献
64.
Pyrethrins Protect Pyrethrum Leaves Against Attack by Western Flower Thrips, <Emphasis Type="Italic">Frankliniella occidentalis</Emphasis> 总被引:1,自引:0,他引:1
Yang T Stoopen G Wiegers G Mao J Wang C Dicke M Jongsma MA 《Journal of chemical ecology》2012,38(4):370-377
Pyrethrins are active ingredients extracted from pyrethrum flowers (Tanacetum cinerariifolium), and are the most widely used botanical insecticide. However, several thrips species are commonly found on pyrethrum flowers
in the field, and are the dominant insects found inside the flowers. Up to 80 % of western flower thrips (WFT, Frankliniella occidentalis) adults died within 3 days of initiating feeding on leaves of pyrethrum, leading us to evaluate the role of pyrethrins in
the defense of pyrethrum leaves against WFT. The effects of pyrethrins on WFT survival, feeding behavior, and reproduction
were measured both in vitro and in planta (infiltrated leaves). The lethal concentration value (LC50) for pyrethrins against WFT adults was 12.9 mg/ml, and pyrethrins
at 0.1 % (w/v) and 1 % (w/v) had significantly negative effects on feeding, embryo development, and oviposition. About 20-70 %
of WFT were killed within 2 days when they were fed chrysanthemum leaves containing 0.01-1 % pyrethrins. Chrysanthemum leaves
containing 0.1 % or 1 % pyrethrins were significantly deterrent to WFT. In a no-choice assay, the reproduction of WFT was
reduced significantly when the insects were fed leaves containing 0.1 % pyrethrins, and no eggs were found in leaves containing
1 % pyrethrins. Our results suggest that the natural concentrations of pyrethrins in the leaves may be responsible for the
observed high mortality of WFT on pyrethrum. 相似文献
65.
Marcus Heinze Sandra Starke Marcel Händler Hartmut Komber Marco Drache Norbert Moszner Brigitte Voit Doris Pospiech 《应用聚合物科学杂志》2019,136(48):48256
We demonstrate in this study that the combination of modern inline monitoring methods [here: inline nuclear magnetic resonance (NMR)] with simulations gains more exact and profound kinetic results than previously used methods like linearization without that combination. The 1H-NMR spectroscopic data (more than 100 data points) are used to construct the copolymerization diagram. The reactivity ratios are obtained applying the van Herks nonlinear least square method. The examination of the radical copolymerization of 2-hydroxyethyl methacrylate (HEMA) with (2-{[2-(ethoxycarbonyl)prop-2-en-1-yl]oxy}ethyl) phosphonic acid (ECPPA) as important adhesive monomer used in dentistry yields reactivity ratios of rHEMA = 1.83; rECPPA = 0.42. The copolymerization diagram reflects nonideal, non-azeotropic copolymerization. The sequence distribution of the obtained by Monte Carlo simulation indicates the generation of statistical copolymers. As an important finding, it is demonstrated that the repeating units responsible for etching and adhesion are arranged over the whole polymer chain, which is necessary to achieve proper functionality. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48256. 相似文献
66.
Fabienne Levi-Acobas Dr. Pascal Röthlisberger Dr. Ivo Sarac Dr. Philippe Marlière Prof. Dr. Piet Herdewijn Dr. Marcel Hollenstein 《Chembiochem : a European journal of chemical biology》2019,20(24):3032-3040
The formation of artificial metal base pairs is an alluring and versatile method for the functionalization of nucleic acids. Access to DNA functionalized with metal base pairs is granted mainly by solid-phase synthesis. An alternative, yet underexplored method, envisions the installation of metal base pairs through the polymerization of modified nucleoside triphosphates. Herein, we have explored the possibility of using thiolated and pKa-perturbed nucleotides for the enzymatic construction of artificial metal base pairs. The thiolated nucleotides S2C, S6G, and S4T as well as the fluorinated analogue 5FU are readily incorporated opposite a templating S4T nucleotide through the guidance of metal cations. Multiple incorporation of the modified nucleotides along with polymerase bypass of the unnatural base pairs are also possible under certain conditions. The thiolated nucleotides S4T, S4T, S2C, and S6G were also shown to be compatible with the synthesis of modified, high molecular weight single-stranded (ss)DNA products through TdT-mediated tailing reactions. Thus, sulfur-substitution and pKa perturbation represent alternative strategies for the design of modified nucleotides compatible with the enzymatic construction of metal base pairs. 相似文献
67.
Freddy Boscn Marcel Meeuwisse Dirk Mestach Maria Paulis Maria Jesus Barandiaran Silfredo Javier Bohrquez 《大分子材料与工程》2019,304(7)
The benefits of polymerizing very insoluble monomers in aqueous media, avoiding the use of energy‐intensive procedures, by implementing two novel synthesis techniques based on the emulsifier combination in emulsion polymerization and on miniemulsification by phase inversion temperature are investigated. The performance of standalone polymers consisting of monomers, namely lauryl methacrylate, isobornyl acrylate, and 1H,1H,2H,2H‐perfluorodecyl acrylate, and of formulated binders with these monomers incorporated either through blending or in situ polymerization, is evaluated with special emphasis on their water‐barrier properties (e.g., uptake, whitening, immersion, and vapor resistance) and on their chemical resistance. The performance of the standalone polymers is found to be similar to that of polymers prepared by high‐shear miniemulsion polymerization, while the performance of the formulated binders is generally superior to a commercial coating formulation based on a binder recommended for water resistance. 相似文献
68.
A new crystalline ground state was discovered in the Au–Si system through first-principles electronic structure calculations. The new structure was found using the experimentally and theoretically determined local atomic structure in the liquid as a guide for the solid state. Local atomic structure in the liquid was matched with that for all known crystal structures as compiled in the Pauling File structural database. The best matching crystalline structures were then explicitly calculated using first-principles methods. Most candidate crystal structures were found to be close, but above the enthalpy of a composition weighted average of the face-centered cubic Au and diamond structure Si terminal phases, but one crystal structure was more stable than the terminal phases by about 10 meV atom–1 at T = 0 K. As first-principles simulations of local structure are feasible for most liquid alloys, the present methodology is applicable to other alloys lying near a eutectic composition. 相似文献
69.
Marcel Gratz Markus Wehring Petrik Galvosas Frank Stallmach 《Microporous and mesoporous materials》2009,125(1-2):30
The diffusional behavior of selected hydrocarbons adsorbed in NaX zeolites were investigated with pulsed magnetic field gradient (PFG) NMR methods in two different ways. First, the exchange time τexch of n-pentane between the interior and the exterior of the zeolite crystals was determined by two-dimensional diffusion exchange spectroscopy. The results were compared to the mean life time τintra as obtained by fast NMR tracer desorption method. Second, the diffusion of a propylene–propane mixture adsorbed in the zeolite was studied by Fourier transform PFG NMR, thus employing the chemical shift of the individual organic constituents as a second dimension for a selective evaluation of the PFG NMR signal decays and the subsequent extraction of corresponding diffusion coefficients. Modifications of NMR pulse sequences necessary for the application of ultra-high pulsed magnetic field gradients of up to in microporous materials are briefly discussed for both kind of experiments. 相似文献
70.
Christian Eberle Johannes A. Burkhard Bernhard Stump Marcel Kaiser Reto Brun Prof. Dr. R. Luise Krauth‐Siegel Prof. Dr. François Diederich Prof. Dr. 《ChemMedChem》2009,4(12):2034-2044
Trypanothione reductase (TR) is a flavoenzyme unique to trypanosomatid parasites and a target for lead discovery programs. Various inhibitor scaffolds have emerged in the past, exhibiting moderate affinity for the parasite enzyme. Herein we show that the combination of two structural motifs of known TR inhibitors — diaryl sulfides and mepacrine — enables the simultaneous addressing of two hydrophobic patches in the active site. The binding efficacy of these conjugates is enhanced over that of the respective parent inhibitors. They show Kic values for the parasite enzyme down to 0.9±0.1 μm and exhibit high selectivity for TR over human glutathione reductase (GR). Despite their considerable molecular mass and in some cases permanent positive charges, in vitro studies revealed IC50 values in the low micromolar to sub‐micromolar range against Trypanosoma brucei rhodesiense and Trypanosoma cruzi, as well as the malaria parasite Plasmodium falciparum, which lack trypanothione metabolism. The inhibitors exhibit strong fluorescence due to their aminoacridine moiety. This feature allows visualization of the drugs in the parasite where high accumulation was observed by fluorescence microscopy even after short exposure times. 相似文献