Application of Asymmetric Model in Analysis of Fluorescence Spectra of Biologically Important Molecules

Having a valid mathematical model for structureless emission band shapes is important when deconvoluting fluorescence spectra of complex molecules. We propose a new asymmetric model for emission spectra of five organic molecules containing aromatic ring: catechol, coniferyl alcohol, hydroquinone, phenylalanine and tryptophan. For each molecule, a series of emission spectra, varying in excitation wavelength, were fitted with the new model as well as with two other analytical expressions: log-normal, described previously in the literature, and sigmoid-exponential. Their deconvolution into two, three and four Gaussian components was also performed, in order to estimate the number of symmetric components needed to obtain a better fitting quality than that of the asymmetric models. Four subtypes of the new model, as well as the log-normal one, did not differ significantly in their fitting errors, while the sigmoid-exponential model showed a significantly worse fit. Spectra of two mixtures: hydroquinone–coniferyl alcohol and hydroquinone–tryptophan were deconvoluted into two asymmetric and four Gaussian components. Positions of asymmetric components of mixtures matched those of separate molecules, while Gaussian did not. Component analysis of a polymer molecule, lignin, was also performed. In this more complex case asymmetric and Gaussian components also grouped in alternating positions.     

Statistical mixture design optimization of extraction media and mobile phase compositions for the characterization of green tea

The influence of different solvents on the extraction medium and the RP-HPLC mobile phase composition were investigated by statistical mixture designs to optimize solvent proportions to prepare the fingerprint of a medicinal herbal extract. For modeling, the number of peaks was used as a measure of fingerprint information. The optimum compositions of solvent to extract chemical substances from green tea and for mobile phase chromatographic analysis were ethyl acetate/ ethanol/dichloromethane (20:5:75 v/v/v) and MeOH/ACN/water (7.5:57.5:35 v/v/v), respectively. This system results in 26 peaks in the chromatographic fingerprint. These results show that an incorrect choice of modifiers for mobile phase composition and solvent extraction hampers the detection of a maximum number of peaks and produces a poor chromatographic fingerprint.     

Mathematical modeling of flow and kinetics in a reactor for dilute-acid hydrolysis of cellulose particles

Amathematical model to simulate the dilute-acid hydrolysis process of cellulose particles is presented. In this model, the mass is treated as a mixture of different components. A test case is considered for which transport equations for components are developed and solved together with the momentum equation for the fluid flow. To solve the model equations, a commercially available flow solver was used. All input data were taken from previously published works. For the small static mixer considered as test geometry, the result, in terms of the conversion of the cellulose particles, was reasonable. With input parameters that are relevant to a plant-size reactor, the model can be used to predict the conversion of both cellulose and hemicellulose particles.     

On the number of droplets in aerosols

The number of droplets which may be formed with a supersaturated vapor in presence of a gas cannot exceed a number proportional to (p_v−p_v0)⁴ where p_v and p_v0 denote at the same temperature the pressure of the supersaturated vapor–gas mixture and the pressure of the saturated vapor–gas mixture. The energy necessary to the droplet formation is also bounded by a number proportional to (p_v−p_v0)².     

Condensation of a zeotropic CFC 114-CFC 113 refrigerant mixture in the annulus of a double-tube coil with an enhanced inner tube

Local heat transfer and pressure drop measurements were made during condensation of a zeotropic CFC114-CFCll3 refrigerant mixture in the annulus of a double-tube coil consisting of three U-bends and four straight lengths. The inner tube is a 19.1-mm O.D. corrugated copper tube with wire fins soldered onto the outer surface and the inner diameter of the outer duct is 25.0 mm. The vapor-phase mass transfer coefficient exhibited a sawtooth behavior with the U-bends showing higher coefficients than the straight lengths. The frictional pressure gradient data agreed well with a previously developed empirical equation for the condensation of pure refrigerants. A prediction method for the condensation heat transfer rate was proposed on the basis of the correlations of the vapor-phase mass transfer coefficient and heat transfer coefficient of the condensate film. The heat transfer data were correlated by the present method to a mean absolute deviation of 12.9%.     

Rheological studies of coal-oil mixtures

Summary Samples of stable coal-oil mixtures were prepared with coal concentrations ranging from 30–50% by weight. Extensive rheological data were obtained using capillary and cone-plate viscometers for samples of coal-oil mixtures and fuel-oil which served as a reference fluid. Viscosity measurements show coal-oil mixtures to be shear-thinning suspensions, i.e., the viscosity decreases moderately with increasing shear rates. In the concentration range of 30–40% coal, the coal-oil mixture shows a predominantly Newtonian behavior. For mixtures with coal concentrations higher than 40%, a yield point was observed. The study of these samples with the rotating-rod viscometer indicated a migration of coal particles away from the rotating rod with no noticeable rod climbing, thus no evidence of normal stress effects. The rheological data can be represented by any of the three two-parameter models: Power Law, Bingham Plastic, or Casson, with the last two models being more realistic and consistent with the observations.With 9 figures     

多元混合燃料一次引爆实验研究

为了提高多元混合燃料的爆炸威力，采用光测和电测方法，进行了小药量无约束空间三组元固态混合燃料的野外一次引爆实验，得到了该装置条件下较优的燃料配比．实验结果表明，该多元固态混合燃料的云雾分散效果明显优于相同质量的TNT，其爆炸场超压呈衰减-增长-再衰减的变化规律，且具有非常相似的压力场分布、适当增加弹体密度可增强这种固态燃料混合物的爆炸威力。     

Deformation of melts of mixtures of incompatible polymers in a uniform shear field and the process of their fibrillation

Fibril formation in mixtures of incompatible polymers, in this case polyethylene and polystyrene, has been studied with their melt being deformed in a uniform shear field. It has been found that when polyethylene is present in a smaller amount, it may form very long fibrils 5 to 8 μm in diameter in the deformed mixture. The formation of such fibrils is determined by the relationship between the viscosity ratio of the mixture components and shear stress. Also, just as in the case of a nonuniform shear field in a flow through a duct, fibril formation in melts of mixtures of incompatible polymers in a uniform shear field takes place upon reaching a certain shear stress. The lower the ratio between the viscosities of the fibril-forming polymer and the other component, the lower this shear stress.     

多元固相FAE的离散与爆轰的协调研究

一次起爆技术使FAE的两个主要研究方向,即燃料选择与云爆技术,更加紧密地结合在一起,导致对燃料的离散与爆轰的自协调要求更加严格。根据燃料的离散与爆轰的自协调的各制约因素对燃料组分进行选择,再改变燃料组分的质量配比以反馈研究燃料的离散与爆轰的协调性。实验证明所选择的混合燃料的离散与爆轰的协调性决定了超压峰值、正压作用时间、火球覆盖体积等参数,故可根据实际需要通过改变燃料组分配比来调节其协调性以研制不同特点的一次起爆型FAE。另外,基于VB.net平台自编的图像批处理程序,对由高速摄影拍摄到的FAE离散爆轰过程的图像进行处理,效率高、精度高,而且能和Excel、Origin等数据处理软件对接。