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161.
胭脂红荧光光谱机理研究 总被引:2,自引:0,他引:2
胭脂红是食品添加剂中最常用的一种食用色素之一,国家标准对其在食品中添加的剂量有明确的规定,研究其荧光光谱特性具有一定的实际意义。文章分别从理论与实验上对220~400 nm不同激发波长下胭脂红标准溶液的荧光光谱进行了分析,结果表明,胭脂红可以产生较强的荧光,分别在420,530,635,687 nm波长处产生了4个荧光峰,各荧光峰的最佳激发波长也不尽相同,文章给出了相应的荧光光谱图。经研究认为胭脂红荧光是由—OH中的n电子的n→π*跃迁和奈环中的π电子的π→π*跃迁这两类跃迁而产生的,其中420 nm处的荧光峰是由n→π*跃迁产生的, 而530, 635和687 nm这3个波长处的荧光峰是由π→π*跃迁而产生的, 同时其4个波长处的荧光相对强度随激发波长的变化相对改变不同,文章分别从微观机理上给出了一定的解释。研究胭脂红的荧光光谱及其特性可为其他偶氮类色素的荧光光谱研究提供参考,同时能为食品安全检测提供新的方法与途径。 相似文献
162.
163.
We have studied sharp peak landscapes of the Eigen model from a
new perspective about how the quasispecies are distributed in the
sequence space. To analyse the distribution more carefully, we bring
in two tools. One tool is the variance of Hamming distance of the
sequences at a given generation. It not only offers us a different
avenue for accurately locating the error threshold and illustrates
how the configuration of the distribution varies with copying
fidelity $q$ in the sequence space, but also divides the copying
fidelity into three distinct regimes. The other tool is the
similarity network of a certain Hamming distance $d_{0}$, by which we
can gain a visual and in-depth result about how the sequences
are distributed. We find that there are several local similarity optima
around the centre (global similarity optimum) in the distribution of
the sequences reproduced near the threshold. Furthermore, it is
interesting that the distribution of clustering coefficient $C(k)$
follows lognormal distribution and the curve of clustering
coefficient $C$ of the network versus $d_{0}$ appears to be linear
near the threshold. 相似文献
164.
氯代5-氟脲嘧啶卟啉的红外光谱特性的研究 总被引:6,自引:0,他引:6
本文对新合成的对位及间位两类氯代苯基 5 氟脲嘧啶卟啉的红外光谱吸收峰进行了归属和总结 ,讨论了其红外吸收频率随取代基位置变化的规律。指出了苯环上的取代基为电负性强的基团时 ,由于场效应的存在 ,使被测化合物的羰基伸缩振动吸收峰的相对强度发生改变。同时 ,表明了嘧啶环上N原子发生了取代 ,形成单、双取代 5 氟脲嘧啶卟啉化合物的红外光谱特性。 相似文献
165.
许雪松 《原子与分子物理学报》2006,23(1):137-142
应用密度泛函B3LYP/6—31+G(d,p)方法对C8H80-(H2O)n(n=1~5)团簇这种弱相互作用体系进行垒自由度能量梯度优化,得到该系列团簇的稳定蛄构.计算结果表明。在该系列二元团簇中,一方面水分子数目的多少对苯基丙酮分子的结构影响很小,另一方面由于苯基丙酮分子的存在,破坏了团簇中水分子的对称性结构,在团簇内部极力形成O—H—O这样弯曲的有方向性的氢键.对苯基丙酮-水这样结构复杂的团簇,指认光谱的难度非常大,本文只讨论了与C=O有关的振动峰和水分子的对称伸缩振动的最强峰. 相似文献
166.
Jing-tao DongRong-sheng Lu 《Optics and Lasers in Engineering》2012,50(3):502-511
The phase shifting technique is the most widely used approach for detecting the envelope in low coherence interferometry. However, if the phase shifts calibration contains errors, some parasitic fringe structure will propagate into the calculated envelopes and cause imprecision in the envelope peak detection. To tackle these problems, a five-point stencil algorithm is introduced into the phase shifting interference microscopy. Considering the amount of parasitic fringes, envelope peak detection and computational efficiency, the presented approach leads to satisfactory results in performance. In combination with a simple polynomial curve fitting method the proposed algorithm exhibits good performance on envelope peak detection in surface profiling. Both of the simulated results and the experimental results indicated that the presented approach can be taken as an alternative to the currently existing methods used for phase shifting low-coherence interference microscopy. 相似文献
167.
168.
本文报导了用计算机控制的衍射仪(CuKα辐射)测量的金属有机化学汽相沉淀(MOCVD)方法生长的Ⅱ-Ⅵ族应变层超晶格的X射线衍射曲线,观察到了超晶格结构的多级卫星峰,且卫星峰的强度随角度呈周期性变化.对这种卫星峰形成包络的衍射曲线,用X射线运动学衍射理论进行了分析和讨论,这种讨论有助于理解X射线衍射曲线中卫星峰的形成.同时用光致发光和包络峰宽度的方法估算了样品的结构参数. 相似文献
169.
An approach to describe heat transfer in porous media is presented on the basis of the continuous time random walk (CTRW)
framework. CTRW is capable of quantifying both local equilibrium and non-equilibrium heat transfer in heterogeneous domains,
and is shown here to match published experimental data of non-equilibrium thermal breakthrough. It is argued that CTRW will
be particularly applicable to the quantification of heat transfer in naturally heterogeneous geological systems, such as soils
and geothermal reservoirs. 相似文献
170.
This work described methodology of Sn, Pb, Cd and Zn impurities determination in high-purity graphite at direct atomic absorption spectrometry (AAS) with flame furnace (FF) atomizer. It was evidence that quality of AAS measurements are depended from sample amount, its homogeneity, particle size, as well as calibration procedure and operation parameters of FF atomizer. Prior to analysis the method has been developed and optimized with respect to the furnace heating temperature and flame composition of FF atomizer. Conditions of absorption peak areas (QA) formation to each element were studied on the basis of contribution into its value some of individual parameters of analytes, including mass-transporting process from increasing mass of graphite samples into gas phase. Because particle size and homogeneous distribution of analyte in powdered materials has an enormous influence on accuracy and precision of measurement results, graphite as well as appropriate series of powdered reference standards was previously ground and investigated. Graphite samples to be analyzed and standard reference materials with mass from 0.025 to 0.200 g was previously briquetted as pellet and insert on corresponding hole in furnace. The characteristic mass (g0) of Sn, Pb, Cd and Zn were 0.35, 0.1, 0.008 and 0.025 ng, respectively, and relative standard deviation (Sr) not more than 20%. 相似文献