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991.
Xiaoli Li Guangmin Wu Jun Shen Fan Yang Jue Wang 《Journal of Sol-Gel Science and Technology》2002,25(3):235-242
When designing a cut-off interference filter, extra layers are needed to add on each side of periodic symmetrical multilayer to match the incident medium and the substrate. In this paper, we use sol-gel film with adjustable refractive index as the match layer. The influence of the refractive index and thickness of the match layer on the film system is discussed in detail. As an example, a special filter which is transparent (>80%) at the wavelength 3–5 m and high reflective (>90%) at the wavelength 1.3 m is designed. Finally a series of optimized film parameters are presented. The whole design process is a good reference to the other multilayer special filter made by sol-gel process. 相似文献
992.
In near neutral medium, the resonance Rayleigh scattering (RRS) intensities of an alone cationic surfactant and nucleic acid are very weak. However, when they combine with each other to form a complex, the RRS intensity of the solution is enhanced greatly. In this paper the reactions of five cationic surfactants with nucleic acids have been studied. The results show that the reaction conditions and RRS spectral characteristics of these reactions are similar, but their sensitivities are obviously different. Among them, the sensitivity of cetyldimethyl benzylammonium chloride (CDBAC) with an aryl and large molecular weight is the highest, while that of cetyl-trimethylammonium bromide (CTAB) without aryl and with small molecular weight is the lowest. The detection limits for ctDNA and yRNA of the former are 6.6 and 29.4 ng · mL-1, while that of the latter are 13.3 and 53.6 ng · mL-1. The method has better selectivity and can be applied to the determination of trace amounts of nucleic acids. Furthermore, i 相似文献
993.
[reaction: see text] New affinity reagents were synthesized using alkene metathesis to directly modify the MeBmt side chain of cyclosporin A. The reagents were used to detect novel cyclophilins from cellular extracts. 相似文献
994.
The reaction of a nickel dithiolene complex (1) and ethylene is a two-step process, in which the trans-product (2) forms first in the direct addition of the olefin to 1, while the more thermodynamically stable cis-product (3) involves isomerization of 2. The introduction of electron-withdrawing groups (cyano or trifluoromethyl) not only significantly lowers the activation energy (TS1) for the formation of trans-product, but it also strongly stabilizes the products (2, 3) such that they are favored by the free energy. However, these substituents leave the barrier for the conformational transformation step (TS2) nearly unchanged. On reduction, the previously favored adduct is now strongly disfavored. 相似文献
995.
996.
Qi JH Zhang XY Zhang RS Liu MC Hu ZD Xue HF Fan BT 《SAR and QSAR in environmental research》2000,11(2):117-131
It is proposed for the first time a method of prediction of the programmed-temperature retention times of components of naphthas in capillary gas chromatography using artificial neural networks. People are used to predict the programmed-temperature retention time using many formulas such as the integral formula, which requires that four parameters must be determined by calculation or experiments. However the results obtained by the formula are not so good to meet the demand of industry. In order to predict retention time accurately and conveniently, artificial neural networks using five-fold cross-validation and leave-20%-out methods have been applied. Only two parameters: density and isothermal retention index were used as input vectors. The average RMS error for predicted values of five different networks was 0.18, whereas the RMS error of predictions by the integral formula was 0.69. Obviously, the predictions by neural networks were much better than predictions by the formula, and neural networks need fewer parameters than the formula. So neural networks can successfully and conveniently solve the problem of predictions of programmed-temperature retention times, and provide useful data for analysis of naphthas in petrochemical industry. 相似文献
997.
A rapid and sensitive flow-injection kinetic spectrophotometric method is proposed for the determination of ascorbic acid. The procedure is based on the inhibiting effect of ascorbic acid on the enhancing effect of oxalate on the potassium dichromate-potassium iodide/rhodamine 6G system. The detection limit and linear ranges are 0.08 and 0.10-4.00 microg/ml, respectively. The relative standard deviation of 11 replicate measurements is less than 2.0%. This method has been successfully used to determine ascorbic acid in pharmaceuticals, tomatoes and oranges. 相似文献
998.
系统地研究了Gd掺杂对Bi2Sr2Ca1-xGdxCu2Oy单晶超导电性及各向异性电阻率的影响.Tc满足Tc/Tc,max=1-82.6(ax+b)2,并随Gd含量的增加而下降,这是由于Gd掺杂引起载流子浓度减小所导致.在x≥0.19时,ρab(T)在Tc附近有类半导体行为,dρab/dT随Gd含量增大而增大.ρc(T)呈半导体行为,并可用唯象公式ρc(T)=(a/T)exp(Δ/T)+bT+c加以描述.电阻率各向异性ρc/ρab随掺杂浓度增大而增大. 相似文献
999.
It is shown that the multifractal property is shared by both Lyapunov exponents and dual Lyapunov exponents related to scaling functions of one-dimensional expanding folding maps. This reveals in a quantitative way the complexity of the dynamics determined by such maps. (c) 1999 American Institute of Physics. 相似文献
1000.
The oscillation of a delay difference equationis studied and the necessary and sufficient condition for all positive solutions of (E) to oscillate about its positive equilibrium is obtained. 相似文献