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51.
Frederik Detobel Veronika Fekete Wim De Malsche Selm De Bruyne Han Gardeniers Gert Desmet 《Analytical and bioanalytical chemistry》2009,394(2):399-411
The present paper provides a detailed analysis of the analyte-wall adsorption effects in nanochannels, including a random
walk study of the analyte-wall collision frequency, and uses these insights to estimate wall desorption times from chromatographic
experiments in nanochannels. Using coumarin dye analytes and using a methanol/water mixture buffered at pH 3 in 120-nm deep
channels, the surface desorption times on naked fused-silica glass were found to be maximally of the order of 60 to 150 μs,
while they were found to be on the order of 100 to 500 μs on a hydrophobically coated wall. These nonzero adsorption and desorption
times lead to an additional band broadening when conducting chromatographic separations. Shear-driven flows, requiring a noncoated
moving wall and a stationary coated wall, intrinsically turn out to be more prone to this effect than pressure-driven or electro-driven
flows for example. The present study also shows that, interestingly, the number of analyte-wall collisions increases with
the inverse of the channel depth and not with its second power, as would be expected from the Einstein–Smoluchowski relationship
for molecular diffusion. 相似文献
52.
Boleslaw Grabowski 《Pramana》1987,29(5):455-460
The impact broadening by charged electron gas is calculated. A proper account of the Debye screening has been taken as also
the curvilinearity of the perturber’s trajectories. The results have been given in the form of graphs for a ready comparison
with earlier results. 相似文献
53.
The complex nature of filling factor ν = 0 of monolayer graphene is studied in magnetotransport experiments. As a function of perpendicular magnetic field a metal-insulator transition is observed, which is attributed to disorder-induced Landau level broadening in the canted antiferromagnetic phase. In the metallic regime a separation of the zeroth Landau level appears and signs of the quantum spin Hall effect are seen near ν = 0. In addition to local transport, nonlocal transport experiments show results being consistent with helical edge transport. 相似文献
54.
An overview of spectroscopic diagnostics techniques for low temperature plasmas is presented with an emphasis to electron number density — Ne measurement. Stark broadening of non-hydrogenic atom and positive ion spectral lines is given. The attention is drawn to experimental techniques used for line intensity and line profile measurement. Self-absorption test, importance of Abel inversion, deconvolution of experimental line profiles and measurement of line asymmetry are treated in some detail in order to improve Ne measurements. Finally the sources of theoretical and experimental Stark broadening data are reviewed and some details discussed. 相似文献
55.
Xavi Illa Wim De Malsche Han Gardeniers Gert Desmet Albert Romano-Rodríguez 《Journal of chromatography. A》2010,1217(37):5817-5821
An experimental study of a micromachined non-porous pillar array column performance under non-retentive conditions is presented. The same pillar structure has been fabricated in cyclo-olefin polymer (COP) chips with three different depths via hot embossing and pressure-assisted thermal bonding. The influence of the depth on the band broadening along with the already known contribution arising from the top and bottom cover plates has been studied. The experimental results exhibit reduced plate heights as low as 0.2, which are in agreement with the previous experimental work. Moreover, the constant values of the reduced Van Deemter expression are also in accordance with the previous studies. A more exhaustive study of the C-term band broadening is also presented, showing that comparing the space between the pillars with different open tubular rectangular channels offers a good estimation of the C-term band broadening that is obtained experimentally. These experimental results, hence, confirm that micromachined pillar array columns fabricated in COP can achieve the same performance as the ones fabricated in silicon for the presently studied pillar channel design. 相似文献
56.
M.A. Koshelev 《Journal of Quantitative Spectroscopy & Radiative Transfer》2011,112(3):550-552
Broadening and shifting of the 211-202 transition of H216O, H217O, H218O by pressure of water, nitrogen and oxygen were precisely measured at room temperature using spectrometer with radio-acoustic detection of absorption. Shift parameters for all studied lines as well as broadening parameters of H217O, H218O lines were measured for the first time. Comparison of obtained results with previously known experimental and theoretical data is presented. 相似文献
57.
O.M. Lyulin I. Morino R. Kumazawa 《Journal of Quantitative Spectroscopy & Radiative Transfer》2011,112(3):531-539
The absorption spectra of methane at different path lengths and different pressures for three temperatures 180, 240 and 296 K have been recorded in the 5556-6166 cm−1 region using the Bruker IFS 120 HR and 125 HR high-resolution Fourier transform spectrometers. The multispectrum fitting procedure has been applied to these spectra to recover the spectral line parameters. The main goal of this procedure was the determination of self-broadening and self-pressure-induced shift coefficients and the exponents of their temperature dependences. These parameters have been derived for 406 assigned lines with good values of the signal to noise ratio. The rotational dependence of these parameters is discussed. 相似文献
58.
测量了磁性纳米Fe3O4颗粒的X射线衍射谱(XRD)、正电子湮没寿命谱(PALS)和符合多普勒展宽谱(CDBS),研究了不同压力和退火温度对磁性纳米Fe3O4颗粒物相、电子结构、缺陷及电子动量分布等的影响. XRD,PALS,CDBS测量结果表明:纳米Fe3O4颗粒的缺陷浓度随压力的增加而增大,但物相和缺陷类型并未发生变化;磁性纳米Fe3O4<
关键词:
正电子
3O4')" href="#">Fe3O4
寿命谱
多普勒展宽谱 相似文献
59.
60.