Diffusion density

Mullin, J.W. and Osman, M.M. Diffusivity, density, viscosity and refractive index of nickel ammonium sulfate aqueous solutions, J. Chem. Eng. Data, 12(4) 517-518, 1967. 

A modem description of a conventional hydrogen bond as well as its older, more accurate definition are based on Bader s theory of atoms in molecules (AIM theory) [4]. Bader considers matter a distribution of charge in real space of point-like nuclei embedded in the diffuse density of electron charge, p(r). All the properties of matter are manifested in the charge distribution and the topology... 

Not surprisingly, formalisms with very diffuse density functions tend to yield large electrostatic moments. This appears, in particular, to be true for the Hirshfeld formalism, in which each cos 1 term in the expansion (3.48) includes diffuse spherical harmonic functions with / = n, n — 2, n — 4,... (0, 1) with the radial factor rn. For instance when the refinement includes cos4 terms, monopoles and quadrupoles with radial functions containing a factor r4 are present. For pyridin-ium dicyanomethylide (Fig. 7.3), the dipole moment obtained with the coefficients from the Hirshfeld-type refinement is 62.7-10" 30 Cm (18.8 D), whereas the dipole moments from the spherical harmonic refinement, from integration in direct space, and the solution value (in dioxane), all cluster around 31 10 30 Cm (9.4 D) (Baert et al. 1982). 

An eqnation has been derived relating the effective diffusivity of porous foodstuffs to various physical properties such as molecular weight, bulk density, vapor space permeability, water activity as a function of material moisture content, water vapor pressure, thermal conductivity, heat of sorption, and tanperature [80]. A predictive model has been proposed to obtain effective diffusivities in cellular foods. The method requires data for composition, binary molecular diffusivities, densities, membrane and cell wall permeabilities, molecular weights, and water viscosity and molar volume [81]. The effect of moisture upon the effective diffusivity is taken into account via the binding energy of sorption in an equation suggested in Ref. [77]. 

The thermodynamic properties of UC2 have been studied by several scientists. Coninck et al. (1976) conducted experiments on UC2 and provided correlations for the calculation of the thermal diffusivity, thermal conductivity, and emissivity of UC2 as functions of temperature. Coninck et al. (1976) used the modulated electron beam technique in order to determine the thermal diffusivity of UC2 samples. In this technique, an electron gun is used to bombard a material in the form of a thin solid plate from one face. The electron gun is modulated to vary sinusoidally as a function of time. The phase difference between the temperature fluctuations of the two faces of the plate is measured, which is used to determine the thermal diffusivity of the material (Wheeler, 1965). Then, thermal conductivity is calculated as the multiplication of thermal diffusivity, density, and speciflc heat as shown in Eq. [18.3]. 

Tsuchiya et al. (2001) calculated the thermal conductivity of U—ZrH for hydrogen-to-zirconium ratios between 1.6 and 2.0 (1.6 experimentally measured the thermal diffusivity of ZrHjc and calculated the thermal conductivity based on the relationship among the thermal diffusivity, density, and specific heat. Further, they calculated the thermal conductivity of U—ZrH c using the rule of mixture as expressed in Eq. [18.57]. InEq. [18.57], V,-and ki are the volume fraction and thermal conductivity of the constituent phase i. 

While some studies have been earned out on the strueture analysis of the systems involving calcium ions with caffeine using speetroseopy techniques (for example, Fourier Transform Infrared (FTIR) and UV-visible speetroscopies used to determine the cation binding mode and the assoeiation constants, AT(caffeine-Ca) = 29.8 M ) [1], few have taken into account the transport behavior of those complex chemical systems. Therefore, the characterization of the transport and thermodynamic properties (diffusion, density and viscosity) in solutions of calcium chloride in the presence of caffeine is important both for fundamental reasons, for understanding the nature of the structure of those aqueous electrolytes, and for practical application in fields such medicine and pharmaey. 

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