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Using the approach of Rulla (1996 SIAM J. Numer. Anal. 33, 68-87)for analysing the time discretization error and assuming moreregularity on the initial data, we improve on the error boundderived by Barrett and Blowey (1996 IMA J. Numer. Anal. 16,257-287) for a fully practical piecewise linear finite elementapproximation with a backward Euler time discretization of amodel for phase separation of a multi-component alloy. 相似文献
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W. G. J. H. M. van Sark P. L. T. M. Frederix D. J. van den Heuvel A. A. Bol J. N. J. van Lingen C. de Mello Donegá H. C. Gerritsen A. Meijerink 《Journal of fluorescence》2002,12(1):69-76
Room-temperature time-resolved luminescence measurements on single CdSe/ZnS quantum dots (QDs) are presented. Fluorescence emission spectra were recorded over periods of up to 30 minutes with a time resolution as small as 6 ms. For QDs in ambient air, a clear 30–40 nm blue shift in the emission wavelength is observed, before the luminescence stops after about 2–3 minutes because of photobleaching. In a nitrogen atmosphere, the blue shift is absent while photobleaching occurs after much longer times (i.e., 10–15 minutes). These observations are explained by photoinduced oxidation. The CdSe surface is oxidized during illumination in the presence of oxygen. This effectively results in shrinkage of the CdSe core diameter by almost 1 nm and consequently in a blue shift. The faster fading of the luminescence in air suggests that photoinduced oxidation results in the formation of non-radiative recombination centers at the CdSe/CdSeOx interface. In a nitrogen atmosphere, photoinduced oxidation is prevented by the absence of oxygen. Additionally, a higher initial light output for CdSe/ZnS QDs in air is observed. This can be explained by a fast reduction of the lifetime of the long-lived defect states of CdSe QDs by oxygen. 相似文献
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Fluorescence lifetime imaging of oxygen in living cells 总被引:1,自引:0,他引:1
H. C. Gerritsen R. Sanders A. Draaijer C. Ince Y. K. Levine 《Journal of fluorescence》1997,7(1):11-15
The usefulness of the fluorescent probe ruthenium tris(2,2′-dipyridyl) dichloride hydrate (RTDP) for the quantitative imaging
of oxygen in single cells was investigated utilizing fluorescence lifetime imaging. The results indicate that the fluorescence
behavior of RTDP in the presence of oxygen can be described by the Stem-Volmer equation. This shows that fluorescence quenching
by oxygen is a dynamic quenching process. In addition, it was demonstrated that the fluorescence lifetime of RTDP is insensitive
to pH, ion concentration, and cellular contents. This implies that a simple calibration procedure in buffers can be used to
quantify oxygen concentrations within cells. First fluorescence imaging experiments on J774 macrophages show a nonuniform
fluorescence intensity and a uniform fluorescence lifetime image. This indicates that the RTDP is heterogeneously partitioned
throughout the cells, while the oxygen concentration is constant. 相似文献
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Electron Stimulated Desorption (ESD) of O+ ions from oxygen-covered Ni(100) has been investigated at 390 K and 500 eV primary energy. The ion energy distribution is found to peak at 7.5 eV and to extend to 11 eV, over our whole exposure range (0–1000 L). The 7.5 eV peak height as a function of exposure shows that desorption takes place both in the chemisorption and the oxidation region. Emission of O+ occurs preferentially along the surface normal, with a base width of ≈ 60°. No azimuthal structure is observed. Additional electron energy dependent measurements clearly show a threshold near the oxygen 2s level. 相似文献
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Back Cover: Integrated Transmission Electron and Single‐Molecule Fluorescence Microscopy Correlates Reactivity with Ultrastructure in a Single Catalyst Particle (Angew. Chem. Int. Ed. 1/2018) 下载免费PDF全文
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Integrated Transmission Electron and Single‐Molecule Fluorescence Microscopy Correlates Reactivity with Ultrastructure in a Single Catalyst Particle 下载免费PDF全文
Frank C. Hendriks Sajjad Mohammadian Dr. Zoran Ristanović Dr. Sam Kalirai Dr. Florian Meirer Prof. Dr. Eelco T. C. Vogt Dr. Pieter C. A. Bruijnincx Prof. Dr. Hans C. Gerritsen Prof. Dr. Bert M. Weckhuysen 《Angewandte Chemie (International ed. in English)》2018,57(1):257-261
Establishing structure–activity relationships in complex, hierarchically structured nanomaterials, such as fluid catalytic cracking (FCC) catalysts, requires characterization with complementary, correlated analysis techniques. An integrated setup has been developed to perform transmission electron microscopy (TEM) and single‐molecule fluorescence (SMF) microscopy on such nanostructured samples. Correlated structure–reactivity information was obtained for 100 nm thin, microtomed sections of a single FCC catalyst particle using this novel SMF‐TEM high‐resolution combination. High reactivity in a thiophene oligomerization probe reaction correlated well with TEM‐derived zeolite locations, while matrix components, such as clay and amorphous binder material, were found not to display activity. Differences in fluorescence intensity were also observed within and between distinct zeolite aggregate domains, indicating that not all zeolite domains are equally active. 相似文献