Mineral Phase Transformation

The score images showed a significant overlap between the two factors. However, in an 18-month-old mouse, only one normal mineral factor was observed after fracture, either because aging might prevent mineral phase transformations, or because the damage did not propagate far enough to be observed. 

Key words laterite ore, limonite, dehydration, sintering, mineral phase transformation... 

Penn R L and Banfieid J F 1999 Formation of rutiie nuciei at anatase (112) twin interfaces and the phase transformation mechanism in nanocrystaiiine titania Am. Miner. 84 871... 

Spanos, N. and Koutsoukos, P.G., 1998. The transformation of vaterite to calcite effect of the conditions of the solutions in contact with the mineral phase. Journal of Crystal Growth, 191, 783-790. 

Rey, C., Renugopalakrishnan, V., Shimizu, M., Collins, B. and Glimcher, M.J. 1991 A resolution-enhanced Fourier transform spectroscopic study of the environment of the COj ion in the mineral phase of enamel during its formation and maturation. Calcified Tissue International 49 259-268. 

The evolved hardpans (Fig. 1b) are composed by rhythmic alternation of submillimetric goethite-rich (ochreous) and hematite-rich (red) layers. This layering is the result of a complex evolution of the pristine authigenic Fe-oxides and -oxyhydroxides during which the mineral phases are cyclically involved in transformation processes including recrystallization, dissolution and reprecipitation (Carbone etal. 2005). 

Hydrophobic pollutants such as PCBs often partition into lipid rather than into water. The K0w measures this partitioning. This coefficient provides an indication of the degree to which a pollutant accumulates into fatty tissues and any organic phase. This coefficient is especially useful for determining the release of PCBs from mineral oil transformer fluids, and Hawker and Connell [391] pro-... 

Dove MT, Winker B, l slie M, Harris MJ, Salje EKH (1992) Anew interatomic potential model for calcite Applications to lattice-dynamics studies, phase-transformations, and isotope fractionation. Am Mineral 77 244-250... 

Klupinski et al. (2004) conclude that the reduction of nitroaromatic compounds is a surface-mediated process and suggest that, with lack of an iron mineral, reductive transformation induced only by Fe(II) does not occur. However, when C Cl NO degradation was investigated in reaction media containing Fe(II) with no mineral phase added, a slow reductive transformation of the contaminant was observed. Because the loss of C Cl NO in this case was not described by a first-order kinetic model, as in the case of high concentration of Fe(II), but better by a zero-order kinetic description, Klupinski et al. (2004) suggest that degradation in these systems in fact is a surface-mediated reaction. They note that, in the reaction system, trace amounts of oxidize Fe(II), which form in situ suspended iron oxide... 

Reduction by Fe(ll) results in an increase in the amount of iron oxides, which favor further reaction. Such autocatalytic behavior characterizes the oxidation of Fe(II) by and explains C Cl NO reduction by Fe(ll) in the absence of an iron mineral phase. Generalizing this behavior, it can be assumed that Fe(III) colloids derived from Fe(ll) oxidation in subsurface anoxic systems, together with other colloids, affect the environmental persistence of nitroaromatic contaminants. Colon et al. (2006), for example, elucidate factors controlling the transformation of nitrosobenzenes and N-hydroxylanilines, which are the two intermediate... 

Pressure-induced phase transformations are known to occur for a wide range of solids. Bulk Si, for example, has the diamond structure at ambient conditions but converts to the 3-tin structure at pressures around lOOkbar. Figure 2.5 shows how it is possible to use the kinds of information we have calculated in this chapter using DFT to predict the existence of pressure-induced phase transformations. It was essentially this idea that was used to make the geologically relevant predictions of the properties of minerals such as MgSi03 that were mentioned as one of the motivating examples in Section 1.2. 

Ferrihydrite and its phase transformations during heating in the oxidizing and reducing environments. Lith. Miner. Resourc. 

The scope of kinetics includes (i) the rates and mechanisms of homogeneous chemical reactions (reactions that occur in one single phase, such as ionic and molecular reactions in aqueous solutions, radioactive decay, many reactions in silicate melts, and cation distribution reactions in minerals), (ii) diffusion (owing to random motion of particles) and convection (both are parts of mass transport diffusion is often referred to as kinetics and convection and other motions are often referred to as dynamics), and (iii) the kinetics of phase transformations and heterogeneous reactions (including nucleation, crystal growth, crystal dissolution, and bubble growth). 

Table 3-2 Diffusion coefficients of noble gases in aqueous solutions Table 3-3 Ionic porosity of some minerals Table 4-1 Steps for phase transformations Table 4-2 Measured crystal growth rates of substances in their own melt...

The various findings about fluoride and its interaction with the hydroxyapatite at the molecular level show that the relationship is complicated and multifaceted. The broad conclusion from the enormous volume of work that has led to our current understanding of the role of fluoride is that it is overwhelmingly beneficial. It promotes numerous desirable properties in tooth mineral, reducing solubility through action in both the saliva and in the mineral phase, it shifts the demineralisation/remineralisation equilibrium in favour of remineralisation, and through its actions in the solid state, ensures that the kinetically favoured OCP is transformed into the more thermodynamically stable hydroxyapatite. Research continues, and there is no doubt that there is still more to learn about the complexities of the interaction of fluoride with hydroxypatite under physiological conditions. 

F.K. LeGoues, H.I. Aaronson, Y.W. Lee, and G.J. Fix. Influence of crystallography upon critical nucleus shapes and kinetics of homogeneous f.c.c.-f.c.c. nucleation. I. The classical theory regime. In International Conference on Solid—>Solid Phase Transformations, pages 427-431, Warrendale, PA, 1982. The Minerals, Metals and Materials Society. 

Selim et al. (1976a) proposed a mathematical model for potassium reactions and transport in soils. Kinetic reactions were assumed to govern the transformation between solution, exchangeable, nonexchangeable (secondary minerals), and primary mineral phases of potassium shown in Fig. 9.3. 

Mathematical derivations of potassium transport and transformation processes may be formulated as follows. The following new terms can be defined C, concentration of potassium in solution phase Si, amount of potassium in exchangeable phase S2, amount of potassium in nonexchangeable phase S5, amount of potassium in primary mineral phase wPW, pore water velocity Dc, dispersion coefficient and d, depth or distance below soil surface. 

Similarly, the transformations of the nonexchangeable phase (Sy and of the mineral phase (S3) could be expressed, respectively, as... 

The major peculiarities for a diagenetically altered bone are an increase in crystal size and a decrease in protein content [104], thus complementary information on the state of degradation can be obtained by FT-IR (Fourier transform infrared spectroscopy). The characteristic splitting of the double peak at 563-604 cm-1 corresponds to the phosphate vibrations v4 (P04)3- indicating mineral-phase modifications, e.g. changes in crystallinity. A low value for the splitting factor SF indicates a high amount of amorphous material in the mineral phase and was obtained as described in Ref. [105],... 

Ito, E. Takahashi, T. (1987) Ultrahigh-pressure phase transformations and the constitution of the deep mantle. In High-Pressure Research in Mineral Physics. (M. H. Manghnani Y. Syono, eds AGU, Washingon, D.C.), Geophys. Mono., 39, 221-9. 

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