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排序方式: 共有593条查询结果,搜索用时 46 毫秒
501.
Z. G. Hu S. W. Wang Z. M. Huang G. S. Wang Z. H. Zhang W. Lu J. H. Chu 《Thin solid films》2003,440(1-2):190-194
Bi2Ti2O7 thin films have been grown directly on n-type GaAs (1 0 0) by the chemical solution decomposition technique. X-ray diffraction analysis shows that the Bi2Ti2O7 thin films are polycrystalline. The optical properties of the thin films are investigated using infrared spectroscopic ellipsometry (3.0–12.5 μm). By fitting the measured ellipsometric parameter (Ψ and Δ) data with a three-phase model (air/Bi2Ti2O7/GaAs), and Lorentz–Drude dispersion relation, the optical constants and thickness of the thin films have been obtained simultaneously. The refractive index and extinction coefficient increase with increasing wavelength. The fitted plasma frequency ωp is 1.64×1014 Hz, and the electron collision frequency γ is 1.05×1014 Hz, and it states that the electron average scattering time is 0.95×10−14 s. The absorption coefficient variation with respect to increasing wavelength has been obtained. 相似文献
502.
J. B. Varesi J. D. Benson M. Martinka A. J. Stoltz W. E. Mason L. A. Almeida A. W. Kaleczyc P. R. Boyd J. H. Dinan 《Journal of Electronic Materials》2005,34(6):758-761
We have examined the etching of HgCdTe (x=0.2) with bromine/ethylene glycol (Br/EG) solutions. Using a spectroscopic ellipsometer,
we tracked the ellipsometric parameters (ψ and Δ) of the freshly etched HgCdTe surfaces. Parameters ψ and Δ were measured
periodically as these values changed with the surface exposed to air. A second set of Br/EG-etched samples was stored in deionized
(DI) water. We found that DI water effectively preserved the freshly etched HgCdTe surface for a period of several hours.
Comparison with the literature on HgCdTe surface chemistry implies that oxide growth is inhibited on the etched HgCdTe samples
immersed in DI water. Modeling results based on the measured ψ and Δ values agree with this assessment. 相似文献
503.
This article summarizes several approaches for understanding the catalytic chemistry and “structure-surface acidity-reactivity” relationships in a multiplicity of catalytic applications of a continually increasing assemblage of metal-organic frameworks (MOFs) structures. The various spectroscopic techniques for acid-base characterization of MOFs are reviewed. The experimental requirements and the type and nature of probe molecules available are also discussed. Special emphasis is given to the revealing of the surface acid-base effect on the catalytic performance of MOFs. 相似文献
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Shinsuke Nakayama 《Journal of Nuclear Science and Technology》2016,53(1):89-101
Spectroscopic factors for the (d,p) reactions on 12C, 27Al, 40Ca, and 58Ni for incident deuteron energies up to 100 MeV were extracted systematically by fitting theoretical distorted wave Born approximation calculations to the existing experimental data. The extracted spectroscopic factors show similar incident energy dependence for all the target nuclei. An empirical expression describing the energy dependence has been deduced and implemented in a computational code system developed specially for deuteron-induced reactions. The calculation with the code system reproduces the measured 27Al(d,p)28Al cross sections in the incident energy range from the threshold to 20 MeV and the measured double-differential cross sections for (d,xp) reactions on 12C and 58Ni at 56 and 100 MeV fairly well. 相似文献
506.
采用射频磁控溅射技术在Si(111)基片上制备金属锰膜,用椭圆偏振光谱在2.0~4.0 e V光子能量范围内研究了溅射压强对锰膜光学性质的影响.分别用德鲁得-洛伦兹模型以及有效介质模型对椭偏参数进行拟合,结果表明随压强增大薄膜致密度先增大后减少;折射率随压强增大先减少后增大;而消光系数随压强的变化与光子能量有关,在低能量区变化复杂,高能量区随压强增加与折射率规律一致.分析表明上述变化与薄膜的致密度密切相关. 相似文献
507.
Role of the Chemical Environment beyond the Coordination Site: Structural Insight into FeIII Protoporphyrin Binding to Cysteine‐Based Heme‐Regulatory Protein Motifs
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Nishit Goradia Kerstin Galler Prof. Dr. Jürgen Popp Dr. Ute Neugebauer Dr. Oliver Ohlenschläger Prof. Dr. Diana Imhof 《Chembiochem : a European journal of chemical biology》2015,16(15):2216-2224
The importance of heme as a transient regulatory molecule has become a major focus in biochemical research. However, detailed information about the molecular basis of transient heme–protein interactions is still missing. We report an in‐depth structural analysis of FeIII heme–peptide complexes by a combination of UV/Vis, resonance Raman, and 2D‐NMR spectroscopic methods. The experiments reveal insights both into the coordination to the central iron ion and into the spatial arrangement of the amino acid sequences interacting with protoporphyrin IX. Cysteine‐based peptides display different heme‐binding behavior as a result of the existence of ordered, partially ordered, and disordered conformations in the heme‐unbound state. Thus, the heme‐binding mode is clearly the consequence of the nature and flexibility of the residues surrounding the iron ion coordinating cysteine. Our analysis reveals scenarios for transient binding of heme to heme‐regulatory motifs in proteins and demonstrates that a thorough structural analysis is required to unravel how heme alters the structure and function of a particular protein. 相似文献
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510.
《国际聚合物材料杂志》2012,61(3-4):265-274
Abstract The synthesis of 3-octyl-thiophene, 3,3′-dioctyl-bithiophene and 3,4′,3″-tri(3-octy!)-terthiophene has been carried out by using the cross coupling reaction, catalyzed by nickel. These oligomers were polymerized by chemical oxidative method with FeCl3 and electrochemically. The products were characterized by UV. 1H-NMR, 13C-NMR and GPC. The behavior and optical properties of the polymers obtained by different polymerization methodologies is discussed. 相似文献