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401.
Dohnal P Hejduk M Varju J Rubovič P Roučka Š Kotrík T Plašil R Glosík J Johnsen R 《The Journal of chemical physics》2012,136(24):244304
Measurements in H(3)(+) afterglow plasmas with spectroscopically determined relative abundances of H(3)(+) ions in the para-nuclear and ortho-nuclear spin states provide clear evidence that at low temperatures (77-200 K) para-H(3)(+) ions recombine significantly faster with electrons than ions in the ortho state, in agreement with a recent theoretical prediction. The cavity ring-down absorption spectroscopy used here provides an in situ determination of the para/ortho abundance ratio and yields additional information on the translational and rotational temperatures of the recombining ions. The results show that H(3)(+) recombination with electrons occurs by both binary recombination and third-body (helium) assisted recombination, and that both the two-body and three-body rate coefficients depend on the nuclear spin states. Electron-stabilized (collisional-radiative) recombination appears to make only a small contribution. 相似文献
402.
Karolína ikov Ondej Be
i
ka Vlastimil Maek Klra afov Radek Zboil 《Journal of Raman spectroscopy : JRS》2012,43(6):689-691
Surface‐enhanced resonance Raman scattering (SERRS) spectroscopy is a powerful tool for the selective and sensitive detection of porphyrins. We report a repeatable detection of unperturbed free base 5,10,15,20‐tetrakis(1‐methyl‐4‐pyridyl)21H,23H‐porphine in concentrations as low as 1 × 10–13 M in the final system when Ag nanoparticles prepared by modified Tollens method are employed as Raman scattering amplifiers, i.e. without any further post‐modifications of their surface. Most probably the residues of sugar oxidation present on Ag nanoparticle surface are responsible for the effective protection of 5,10,15,20‐tetrakis(1‐methyl‐4‐pyridyl)21H,23H‐porphine molecules against the metalation by silver. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
403.
Set-Valued and Variational Analysis - Influenced by a recent note by M. Ivanov and N. Zlateva, we prove a statement in the style of Nash-Moser-Ekeland theorem for mappings from a... 相似文献
404.
405.
Elham Avirdi Seyyed Emad Hooshmand Heshmatollah Sepahvand Venkataraman Vishwanathan Indra Bahadur Lebogang Maureen Katata-Seru Rajender S. Varma 《Current Opinion in Green and Sustainable Chemistry》2022
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406.
High-performance liquid chromatography determination of phenolic components in wine using off-line isotachophoretic pretreatment 总被引:1,自引:0,他引:1
The off-line combination of isotachophoresis (ITP) and high-performance liquid chromatography (HPLC) to improve sample pretreatment and determination of phenolic compounds in wine was investigated. The ITP system provided an enhanced sample load capacity and served as a sample clean-up technique, HPLC performed a final separation of the analytes presented in samples. The phenolic components were separated by Discovery RP Amid C16 chromatography column using water-methanol-acetonitrile-orthophosphoric acid gradient. The identification of phenolic compounds was made by comparison of the retention data obtained for the standard mixture, pretreated sample and the sample spiked standard additions. Satisfactory recoveries for all components analysed were observed between 86.1 and 109.2%. 相似文献
407.
Butane-1,4-diol was fluoroalkylated by its photoaddition reactions with hexafluoropropene and perfluoro (propyl vinyl) ether under atmospheric pressure, by which monofluoroalkylated and bis-fluoroalkylated products were obtained. 1,3-Diols were completely unreactive under the conditions. 2,2,2-Trifluoroethanol, tert.butyl alcohol and methyl tert.butyl ether appeared to be inert solvents for the additions while acetonitrile quenched the reactions. The reactivity of perfluoro vinyl ethers was studied (tested) in their photoaddition reactions with alkanols that were less regioselective (up to 7% rel.of regioisomer) in comparison with hexafluoropropene. Surprisingly, photo-supported base-induced nucleophilic monoand bis-addition of butane-1,4-diol onto hexafluoropropene was observed in acetonitrile. 相似文献
408.
Jan Hrbac Vladimir Halouzka Radek Zboril Kyriakos Papadopoulos Theodor Triantis 《Electroanalysis》2007,19(17):1850-1854
In this study we show that nanoparticles of various ferric oxides (hematite, maghemite, amorphous Fe2O3, β‐Fe2O3 and ferrihydrite) incorporated into carbon paste exhibit electro‐catalytic properties towards hydrogen peroxide reduction. The modified paste electrode performances were evaluated and compared with those obtained with Prussian Blue‐modified carbon paste electrode, which represents an excellent chemical mediator towards the H2O2 redox reaction (as widely described in literature). The best catalytic activity was found for carbon paste modified by amorphous ferric oxide with 2–4 nm particle size, which was further tested for possible application as hydrogen peroxide sensor. At pH 7, the limit of detection was 2×10?5 M H2O2 (S/N=3), the calibration curves were linear upto 8.5 mM H2O2 (R2=0.998), the measurement reproducibility (RSD=97%, n=4), the interelectrode reproducibility (RSD=16%, nelectrodes=5) and <3 s response time. 相似文献
409.
The irreversible adsorption of polymers to a two-dimensional solid surface is studied. An operator formalism is introduced
for chemisorption from a polydisperse solution of polymers which transforms the analysis of the adsorption process to a set
of combinatorial problems on a two-dimensional lattice. The time evolution of the number of polymers attached and the surface
area covered are calculated via a series expansion. The dependence of the final coverage on the parameters of the model (i.e.
the parameters of the distribution of polymer lengths in the solution) is studied. Various methods for accelerating the convergence
of the resulting infinite series are considered. To demonstrate the accuracy of the truncated series approach, the series
expansion results are compared with the results of stochastic simulation. 相似文献
410.
Paul Manuel Indra Rajasingh Bharati Rajan Helda Mercy 《Discrete Applied Mathematics》2009,157(7):1486-1495
Grid embeddings are used not only to study the simulation capabilities of a parallel architecture but also to design its VLSI layout. In addition to dilation and congestion, wirelength is an important measure of an embedding. There are very few papers in the literature which provide the exact wirelength of grid embedding. As far as the most versatile architecture hypercube is concerned, only approximate estimates of the wirelength of grid embedding are available. In this paper, we give an exact formula of minimum wirelength of hypercube layout into grids and thereby we solve completely the wirelength problem of hypercubes into grids.We introduce a new technique to estimate the wirelength of a grid embedding. This new technique is based on a Congestion Lemma and a Partition Lemma which we study in this paper. 相似文献