荧光淬灭和加强理论公式合理性的热力学分析

通过荧光法在不同温度下研究了3种第三代头孢新药: 盐酸头孢吡肟、头孢匹胺和头孢唑肟钠与人血清白蛋白(HSA)和牛血清白蛋白(BSA)的作用, 分别应用荧光淬灭和荧光加强理论公式计算了它们的结合常数等, 进而分别计算了它们的热力学函数. 因对应于不同的理论公式得出的K_A值并不完全相同, 由此得到它们相应的热力学参数也有所不同. 本文对这些热力学数据的差异进行了分析比较, 结果表明: 基于荧光加强理论公式(4)获得的热力学数据显示更为合理. 因而我们建议, 即使在研究受体-底物的荧光淬灭反应时, 采用荧光加强理论公式(4)可以获得更符合实际的结果.     

Interrelation between the crystallinity of polysaccharides and water absorption

The maximum sorption of water and its vapors is calculated using experimental data from calorimetric and effusion studies of flax, wood, and cotton cellulose. X-day diffraction is used to determine the crystallinity of cellulose samples. The equations relating crystallinity (X) with maximum sorption and the enthalpy of interaction between cellulose and water are presented. Experimental results and the literature data on water sorption by chitin, chitosan and other polysaccharides show that our equations for calculating crystallinity are correct.     

SULFONATION IN A FALLING FILM REACTOR: COMPARATION OF EXPERIMENTAL RESULTS WITH MATHEMATICAL MODEL PREDICTIONS

A mathematical model is developed to simulate a falling film reactor for sulfonation/sulfation. In the model, the reaction rate is considered to be controlled by the mass transfer in the gas phase or in the liquid phase. The gas phase mass and heat transfers are calculated by empiric equations; in the liquid phase, they are calculated by solving with numerical methods the partial differential equations which describe the system. In these equations, and eddy diffusion is considered, following the Levich's theories

The model results are compared with the experimental results obtained by the authors in a pilot plant, for the dodecylbenzene sulfonation.     

Electrical Properties of the Swollen Particles of Elastic Gels

The distributions of ion concentrations and electric potential at an interface between macromolecular associates and external solutions were calculated by solving nonlinear equations of the theory of electrolytes. The calculated and experimental results were compared.     

Some analysis of the ω-Technique

The ω-Technique is one of a number of ways of improving on the Hückel model by introducing a dependence on atomic orbital populations into the matrix-elements of the effective Hamiltonian. It requires iterative solution of secular equations until the populations calculated from the solutions are consistent with the populations used in setting up the Hamiltonian matrix. We derive simple equations showing how thedeviations of the populations from their final self-consistent values change with successive iterations. The results of consideration of these equations in several special cases, imply that the populations oscillate about their final values on successive iterations, as has actually been found experimentally. This suggests a simple means of speeding up convergence.     

Existence, uniqueness, and calculation of the physically acceptable solution of a particular case of the Sherman equations

When a chemical sample made of N elements is analyzed by using sequential selective excitation by monochromatic X-ray beams and selective measurement of the characteristic X-rays, the production of secondary fluorescence does not interfere with the measurements. This experimental situation leads to a particular simple case of the Sherman equations which can be written in this instance as linear equations. The linear equations thus obtained are shown to be very similar to the equations appearing in the classical models of Beattie and Brissey and of Lachance and Traill. The linear algebra proves the existence of N different sets of solutions, but the Perron Frobenius theorem ensures that there is one and only one physically feasible solution, and also leads to the method for obtaining it. This equation solution method can be extended to the equations appearing when standard samples of pure elements are also measured.The propagation of the errors in the measurements to the errors in the sample concentrations has been calculated and simulated, and the results have shown that the solution is well conditioned.     

A semi-empirical approach for predicting the performance of mixed matrix membranes containing selective flakes

A successful model for mixed matrix membrane performance must address the complex geometry of the problem and accurately treat the diffusion behavior of the host–guest systems being considered. Detailed calculations based on the Maxwell–Stefan equations provide a widely accepted means of treating the diffusion of gases within zeolites. However, a full numerical solution of these equations for a complex mixed matrix membrane geometry does not offer the convenience and transparency that comes with an analytical treatment. At the same time, existing analytical equations which were formulated specifically to address mixed matrix geometry do so under the assumption of very simplistic models for diffusion. Here, an approach is presented for predicting the permeability and selectivity of mixed matrix membranes containing zeolite flakes that combines well-known analytical expressions for mixed matrix membrane performance with Maxwell–Stefan modeling for zeolite diffusion. The constant permeabilities required by the analytical models are calculated by the Maxwell–Stefan equations as a function of operating conditions, and these calculated effective permeabilities are used to predict mixed matrix membrane performance at corresponding operating conditions. The method is illustrated through two case studies: normal- and iso-butane separation by a membrane containing silicalite-1 flakes and carbon dioxide/methane separation by membranes containing CHA-type zeolites. Predictions are compared to experimental results found in the literature for both cases. Also, the applicability of the Maxwell and Cussler analytical models for mixed matrix membrane performance is explored as a function of flake loading and aspect ratio.     

Thermodynamic analysis of fluorescence enhancement and Quenching theory equations

The action of the three kinds of new third generation cephalosporin-class drugs, cefepime hydrochroride, cefpiramide and ceftizoxime with HSA and BSA was studied at different temperatures through the fluorescence method. First, the binding constants were calculated by using fluorescence quenching and enhancement theoretical equations. Their thermodynamic functions were also calculated. Because the K _A corresponding to the different theoretical equations are not completely the same, the thermodynamic parameters calculated are also different. In this paper, the differences among these thermodynamic data obtained from the different theoretical equations were analyzed and the results show that the thermodynamic data deduced from fluorescence enhancement are more reasonable. Thus, we propose that even when the fluorescence quenching action of the acceptorsubstrate is studied, more realistic data can be obtained by using the fluorescence enhancement equation. __________ Translated from Acta Chimica Sinica, 2007, 65(19): 2109–2116 [译自: 化学学报]     

表面活性剂溶液油水界面相平衡研究

以Butler方程为基础,导出了1组通用的界面相平衡计算方程。利用此方程计算了多个实际体系,结果令人满意。根据实验现象及计算结果,提出了一种多组分界面相物理模型并探讨了表面活性物质在油水界面上的相互作用规律,为乳状液、微乳状液等研究提供了有益的信息。     

Kinetic studies on the decomposition of cyano complexes. I. the thermal decomposition of cyanoferrate(II) acids

The formation of HCN from solid iron(II) cyano complex acids is studied by a non-isothermal kinetic method. A derivatograph is used for the measurements and the kinetic parameters are calculated by different methods using the Horowitz—Metzger, Coats—Redfern and Zsako equations. The results are discussed and the kinetic parameters (energy and entropy of activation) are compared with IR and Mössbauer spectroscopic data.     

A study by RISM method of the features of the environment dielectric response on the hydration of monatomic ions

The characteristics of the dielectric response of water to hydration of monatomic ions were studied by the method of numerical solution of the integral equations of the theory of molecular liquids. Response to various charges of one sign was close to linear, but the proportionality factor for the anions is considerably greater than for cations. The results obtained are similar to those calculated by the method of molecular dynamics. The calculation results show the presence of a regular cellular structure of the charge density distribution with a period of about 2.35 Å around the hydrated ions.     

CNDO calculation of polarizabilities including polarization functions in the basis set

Electric polarizabilities are calculated by solving the first- and second-order perturbation equations through a variational procedure. Satisfactory numerical results are obtained for a number of molecules using the CNDO approximation with an extended basis set.     

The effect of a carrier on the residence time of atoms in an arc discharge plasma

The residence time of impurity atoms in an arc discharge has been calculated using the solution of both steady state and non-steady state equations which describe four different mass transport models; conventional diffusion by itself; conventional diffusion together with the movement of ions in an electric field; conventional diffusion together with ambipolar diffusion and conventional diffusion together with both ambipolar diffusion and the movements of ions in an electric field. The best agreement between measured and calculated results is obtained using the model which considers only conventional and ambipolar diffusion. This model also adequately explains the effect of a carrier on the residence time of atoms in the arc discharge.     

液固色谱中溶质保留规律的研究—多元流动相组成对保留值的影响

根据热力学原理和简单的吸附色谱分子模型。本文提出了一个新的液固色谱保留模型，并导出了相应的保留值基本方程，以三元溶剂系统作为展开剂，用薄层色谱实验数据验证了所得方程的正确性。结果显示，计算Ｒｆ值与实验Ｒｆ值完全一致。     

Equation of state of the hard sphere liquid

Using the results of Monte Carlo simulation, equations of state of hard sphere liquids are calculated for 106 values of the fill factor η= 0.005–0.530 (step of 0.005). In the region of liquid phase stability the absolute accuracy of about 0.00001–0.00008 is reached. Correctness of the accuracy estimate is discussed. The results obtained are compared with reported equations of state of the hard sphere liquid.     

Application of power expansion in the thermodynamics of compressible Markovian copolymers

The problem of constructing phase diagrams for a compressible melt of a binary Markovian copolymer is reduced to a set of nonlinear differential equations in partial derivatives with transcendental relationships. Using power expansions, the closed set of nonlinear differential equations is derived. This set allows its further analytical study. Eigenvalues of a linearized system are analyzed, and the boundaries of the thermodynamic stability of melts are defined. Nonlinear equations in normal coordinates are obtained; for symmetric melts, these equations are reduced to a single equation by adiabatic elimination of small-scale variables. Binodal curves are calculated for such solutions of this equation, which correspond to the free energy minimum of melts. Corrections reflecting the effect of melt nonsymmetry are found. The results are applied for copolymers, whose composition is similar to that of homopolymers, diblock copolymers, and random and regularly alternating copolymers. Spinodals and binodals corresponding to microphase separation are constructed.     

Comparison of algorithms for the calculation of molecular vibrational level densities

Level densities of vibrational degrees of freedom are calculated numerically with formulas based on the inversion of the canonical vibrational partition function. The calculated level densities are compared with other approximate equations from literature and with the exact Beyer-Swinehart values, for which a simplified but equivalent version is given. All approximate equations agree at high excitation energies, but our results are vastly superior at low energies for large molecules. The results presented here are therefore of particular relevance for thermal processes of very large molecules, e.g., of biological nature, for which the exact state counting can be prohibitively slow. Furthermore, it is valid for situations where anharmonic motion significantly influences the thermal properties.     

The numerical solution of fujita's integral equation to provide estimates of molecular weight distributions

A standard model of the behavior of polymers under ultracentrifugation results in Fujita's equation for their molecular weight distribution. Fujita's and related equations are examples of Fredholm integral equations of the first kind and are thus ill posed. Two methods are described for solving the equations numerically and hence providing estimates of the molecular weight distribution. The first method involves expanding the distribution in terms of orthogonal polynomials whose coefficients are calculated from estimates of the moments of the distribution. In the second method the distribution is reconstructed by using matrix singular-value decomposition techniques combined with an approximant expressed as a sum of B-splines. The potential and practical limitations associated with the methods are illustrated by numerical results from a series of tests on four problems designed to represent distributions with different modal properties.     

Influence of the fine-structure interaction and of the g-tensor anisotropy on the ESR lineshape of triplet excitons in molecular crystals with two molecules in the unit cell

Recently a set of equations has been derived describing the influence of the quasi-incoherent exciton motion on the ESR lineshape of triplet excitons in molecular crystals with two molecules per unit cell. Starting from these equations in the case of rapid exciton motion analytic expressions for the positions and widths of the ESR lines are calculated by second order perturbation theory taking into account the different orientations of the fine-structure interaction tensors and of the g-tensors at the two inequivalent molecules in the unit cell. Explicit expressions of the angular dependence of these quantities for rotation of the magnetic high-field around the a^?, b^?, c^?-axes of crystals of the anthracene type are given. Finally contact to experimental results is made.     

The analysis of “power window” induced by thermal effect during the microwave heating

The “windows” are often considered as the evidence of microwave non-thermal effect. Here, enzyme catalysis acrylonitrile reaction was carried out and the coupled multiphysics field equations were solved by finite difference time domain (FDTD) method. The temperature curves can be obtained under the different power. Then, the results calculated by chemical reaction kinetic show that the power window of product concentration can be induced by thermal effect. The power window cannot be a criterion of microwave non-thermal effects.