Structure with NaCl concentration

Figure 4. In vitro reconstituted 30 nm chromatin fiber. Dynamic structural changes in the chromatin fiber in the absence (top) or presence (bottom) of linker histone HI with different NaCl concentration were observed by AFM. Nucleosomes were reconstituted on the 106 kb plasmid and then fixed in the buffer containing 50 mM (top left) or 100 mM NaCl (top right). Nucleosomes were well-spread in 50 mM NaCl but attached each other and partially aggregated in 100 mM NaCl. After the addition of histone HI, the thicker fibers were formed. The width of the fibers is 20nm in 50mM NaCl (bottom left) or 30 nm in lOOmM NaCl (bottom right)...

The Li ions were introduced in two different ways either before or after Zr intercalation. The montmorillonite (Weston L-Eccagun) was first exchanged with NaCl (IN) and washed. Two montmorillonites with reduced charge were prepared following the Brindley and Ertem method (13). Part of the Na+ montmorillonite was first saturated with LiCl (IN) and washed. The Li+ clay thus obtained and Na+ clay suspension were stirred for 24 hours at 25°C and dried on glass plate. The films were then heated at 220°C for 24 h in order to allow Li diffusion in the clay structure. Two different Li concentrations (F=0.4 and F=0.6) were used. The Na Li+ modified montmorillonite were dispersed in water acetone solution (1/1). The ZrOCla, 8H2O solution was added to the Na+Li+ montmorillonite (0.02g.l l Zr/Clay=5.CEC). The suspension was stirred with NaOH solution (0.1 N) up to a OH/Zr ratio of 0.5. The final pH of the suspension was 1.85. After two hours of reaction at 40°C the Zr pillared clay was washed up to constant conductivity of the solution, freeze-dried and calcined at different temperatures up to 700°C (Eni-02 and EIII-03). 

The defect structure of Fei O with the NaCl-type structure had been estimated to be a random distribution of iron vacancies. In 1960, Roth confirmed, by powder X-ray diffraction, that the defect structure of wiistite quenched from high temperatures consists of iron vacancies (Vp ) and interstitial iron (Fcj) (there are about half as many FCj as Vpe). This was a remarkable discovery in the sense that it showed that different types of crystal defects with comparable concentrations are able to exist simultaneously in a substance, Roth also proposed a structure model, named a Roth cluster, shown in Fig. 1.84. Later this model (defect complex = vacancy -F interstitial) was verified by X-ray diffraction on a single crystal and also by in-situ neutron diffraction experiments. Moreover, it has been shown that the defect complex arranges regularly and results in a kind of super-structure, the model structure of which (called a Koch-Cohen model) is shown in Fig. 1.85 together with the basic structures (a) and (b). 

In contrast to NaCl or tetramethylammonium bromide, also shown in Fig. 4, the concentration dependence of the density is less marked. However, the slopes of the density curves measured at 20 °C and 35 °C for DADMAC increase with the concentration. This indicates a change of the interaction with water is likely caused by the formation of ordered structures such as associates [32, 37]. The greatest change of the slope is located at approximately 1.5 mol L 1. The influence of this monomer structure formation on the polymerization behavior will be discussed in Sect. 4. The non-linear concentration dependence of the viscosity is illustrated in Fig. 5. Here, a strong increase of this solution parameter is observed at approximately 1.5 mol L 1 indicating a change of intermolecular interactions [32,37]. 

The behavior of surface tension at high ionic strength also can be understood on the basis of changes in ion hydration changes between bulk and interface. The tendency of the structure-breaking ions to accumulate at the surface can lead to a positive surface adsorption. However, if the cations cannot approach the interface, the asymmetry of the ion distributions generates a potential, which repels the anions from the interface, and the total adsorption becomes negative. Consequently, the surface tension increases with electrolyte concentration this occurs for simple salts (NaCl, KC1). If the cations can approach the interface, the accumulation of anions in the vicinity of the interface is also followed by an accumulation of cations,... 

Another option to reach an agreement between theoretical and experimental isotherms is provided by the assumption that the shift observed is due to structural interactions in the film which determines the structural component of disjoining pressure ns, [5,312], In that context it is interesting to estimate the function ln(nexp - ITiheor) on h, presented in Fig. 3.60. It is plotted at different NaCl concentrations under the assumption that at constant ( -potential and at Cei = 10 4 and 10 3 mol dm 3, the DVLO-theory is conformed with. 

The fit of the MSA to activity coefficient data for aqueous electrolyte solutions can be considerably improved if one takes into consideration the decrease in solvent permittivity which accompanies the increase in electrolyte concentration. This phenomenon is clearly related to the effect that ions have on solvent structure and was studied originally in aqueous solutions by Hasted et al. [21, 22]. More recently, data have been collected for a large number of electrolytes by Barthel and coworkers [23]. In the case of NaCl solutions, the change in dielectric permittivity with electrolyte concentrations up to 2 M is given by... 

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