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991.
992.
Joseph R. Lakowicz Ignacy Gryczynski Józef Kuśba Eva Danielsen 《Journal of fluorescence》1992,2(4):247-258
We measured the fluorescence intensity and anisotropy decays of 1,6-diphenyl-1,3,5-hexatriene (DPH)-labeled membranes resulting from simultaneous two-photon excitation of fluorescence. Comparison of these two-photon data with the more usual one-photon measurements revealed that DPH displayed identical intensity decays, anisotropy decays, and order parameters for one- and two-photon excitation. While the anisotropy data are numerically distinct, they can be compared by use of the factor 10/7, which accounts for the two-photon versus one-photon photoselection. The increased time 0 anisotropy of DPH can result in increased resolution of complex anisotropy decays. Global analysis of the one- and two-photon data reveals consistency with a single apparent angle between the absorption and the emission oscillators. The global anisotropy analysis also suggests that, except for the photoselection factor, the anisotropy decays are the same for one-and two-photon excitation. This ideal behavior of DPH as a two-photon absorber, and its high two-photon cross section, makes DPH a potential probe for confocal two-photon microscopy and other systems where it is advantageous to use long-wavelength (680- to 760-nm) excitation. 相似文献
993.
Chemical effects on the K shell fluorescence yields of Fe, Mn, Co, Cr and Cu compounds were investigated. Samples were excited
using 59.5 keV energy photons from a241 Am radioisotope source. K X-rays emitted by samples were counted by a Si(Li) detector with a resolution 160 eV at 5.9 keV.
Chemical effects on the K shell fluorescence yields (ωk) for Fe, Mn, Co, Cr and Cu compounds were observed. The values are
compared with theoretical, semiempirical fit and experimental ones for the pure elements. 相似文献
994.
Gregory R. Lumpkin Katherine L. Smith Mark G. Blackford Reto Gier C. Terry Williams 《Micron (Oxford, England : 1993)》1994,25(6):581-587
In this paper we describe a technique for the determination of 25 elements in natural zirconolite using energy-dispersive analytical electron microscopy (AEM). The method presented here allows one to quantitatively investigate the chemistry of submicron-scale zones in complex oxide minerals. The effects of electron channeling, thickness variability and variations in detector resolution were minimized by using a controlled set of operating procedures and instrument parameters. To provide a high level of accurayy, kATI-factors were determined from standards for most of the 25 elements of interest, including all of the major elements. Each analytical spectrum is reduced to a set of raw peak counts (and errors) using a digital top-hat filter to suppress background followed by multiple least squares fitting of reference spectra. Counting times of 12–15 min per analysis were required to provide suitable counting statistics. Results are presented for zirconolite samples from the contact metamorphic aureole of the Bergell granodiorite intrusion, Switzerland-Italy. A comparison of 43 AEM analyses with 15 analyses obtained by wavelength-dispersive electron probe microanalysis (EPMA) shows that there is excellent agreement between the two data sets in the amounts of individual elements present, chemical trends and overall stoichiometry. An assessment of the combined data set shows that the major substitution mechanisms in the Bergell samples are coupled substitutions involving the M5,6- and M8-sites of the zirconolite structure: M8Ca2+ + M5,6Ti4+→M8REE3+ + M5,6(Al,Fe)3+ and M8Ca2+ + M5,6Ti4+→M8(Th,U)4+ + M5,6 (Mg,Fe)2+. 相似文献
995.
本文通过X-射线衍射分析(XRD),扫描电子显微镜分析(SEM),化学分析光电子能谱分析(ESCA),并结合原子吸收测量,研究了钒在普通石墨管中石磨探针表面上发生的固相化学反应。结果表明,钒化合物在灰化阶段即可转化为热稳定性较高的碳化物,原子化的最后步骤为碳化物的热分解。 相似文献
996.
997.
合成了两种末端碳锭长度不同的水杨醛类希夫碱N-十二烷基(2-羟基-5-硝基苯甲亚胺)和N-十六烷基(2-羟基-5-硝基苯甲亚胺),研究了它们在气-液界面上的成膜性能,并通过紫外、荧光、红外显微镜等光谱手段对它们在LB膜上的性能进行了表征。实验结果表明两种希夫碱分子在LB膜中都形成了J-聚体,末端碳链较长的希夫碱 成膜性能相对较好,并且在膜上也能光致发光,但希夫碱分子的LB膜存在一定的缺陷。 相似文献
998.
Andrea Kühl Dietrich Bergner Hans-J. Ullrich Matthias Schlaubitz Peter Karduck 《Mikrochimica acta》1992,107(3-6):295-302
Parameters of the diffusion of N (up to 0.3 wt.%) in austenitic stainless steels (12 to 19 wt.% Cr, 12 to 16 wt.% Ni, up to 2 wt.% Mo) were determined within the temperature range of 1283–1573K. The small concentration gradients of N were successfully investigated using (1) mechanical serial sectioning technique in combination with either chemical N analysis or X-ray precision lattice parameter determination, and (2) measurements on microsections by means of either electron probe microanalysis or Kossel technique.The diffusion coefficients of N were found to be independent of its concentration. The alloying elements Cr and Mo reduce the N diffusivity in austenitic stainless steels which on the other hand is increased by Ni. 相似文献
999.
荧光猝灭法研究苯乙烯氧化物与DNA的相互作用 总被引:1,自引:0,他引:1
荧光猝灭法是一种可以研究苯化合物与DNA相互作用的动态过程的方法。研究结果表明,苯乙烯氧化物与DNA的相互作用与苯乙烯氧化物浓度的关系服从动力学一级方程。 相似文献
1000.
芦丁与血清白蛋白的作用研究 总被引:19,自引:4,他引:15
采用荧光光谱和紫外光谱研究了抗炎药物芦丁与牛血清白蛋白 (BSA)和人血清白蛋白 (HSA)的相互作用。通过二者荧光光谱的变化 ,求得药物与白蛋白作用的形成常数。探讨了它们之间的主要作用力类型。 相似文献