Activity fluorapatite

Chen N, Pan Y, Weil JA, Nilges MJ (2002b) Electron paramagnetic resonance study of synthetic fiuor-apatite Part 2. Gd at the Cal site, with a neighboring Cal vacancy. Am Mineral 87 47-55 Chenot CF, Kasenga AF, Poppalardo RE. (1981) Depreciation in cerium-activated fluorapatite phosphors. J Lumin 24-25 95-98... 

Kniep R, Simon P (2007) Fluorapatite-Gelatine-Nanocomposites Self-Organized Morphogenesis, Real Structure and Relations to Natural Hard Materials. 270 73-125 Koenig BW (2007) Residual Dipolar Couplings Report on the Active Conformation of Rhodopsin-Bound Protein Fragments. 272 187-216 Kolusheva S, see Jelinek R (2007) 277 155-180... 

Subsequently, the apparent activities of the quasibinary components hydroxyapatite OHA and fluorapatite FA were derived as follows ... 

The data of Table III show that the surface layer of the solid particles is indistinguishable from pure fluorapatite in all equilibrations at x = 0.110, 0.190 and 0.435 and 0.595. However, some equilibrations at x = 0.763 and all at x = 0.868 do deviate significantly from the behavior of pure fluorapatite. A peculiar aspect is that the activity of fluorapatite becomes significantly larger than 1. Simutaneously, the activity of hydroxyapatite approaches unity. This would mean that at all values of x both activities would become smaller than 1, and thus an ideal behavior of the solid solutions would not explain the observed solubility behavior. 

Apparent activities of hydroxyapatie (OHA) and fluorapatite (FA) after equilibration of solid solutions of the formula Ca5(PO4)3F1 xOHx... 

W explains the observed solubility behavior at x = 0.868. However, it does not explain the high activities of fluorapatite found in some of the equilibrations at x = 0.763. In this model W/2.303 RT > 2.0 so that W >1.17. 10 J mol-. Further refinement of this model is possible by independent variation of W- and W2. 

M. Jarlbring, D.E. Sandstrom, O.N. Antzutkin, W. Forsling, Characterzation of active phosphorus surface sites at synthetic carbonate-free fluorapatite using single pulse H, P, and P CP-MAS NMR, Langmuir 22 (2006) 4787 792. 

Fluorapatite activated by Eu in air and in vacuum has been studied (Gaft et al. 1997b). Two main centers appear after activation in air both characterized by the abnormal relative intensity of the Dq-Fq transition at 574 and 579 nm. Activation in a vacuum leads to prominent changes. New lines at 590,618 and 700 nm appear which dominate at Aex = 384 nm (Fig. 5.10). 

The reduction in dental caries as a result of fluoridation of water supplies and use of fluoride containing toothpastes is well known (Shell s and Duckworth 1994). This is clearly linked in part to the fact that the solubility product of fluorapatite is less than that of HAP (Moreno et al. 1977). For a partial replacement of OIT by F ions, the solubility product for Ca5(P04)3(0H)i.xFx is a minimum for x = 0.56 (Moreno et al. 1977). Chow and Banes (2001) and LeGeros (1991) discuss further the effects of F ions on the solubility, rate of dissolution and formation of apatites. Fluoride has also been used in attempts to rebuild bone lost as a result of osteoporosis (see Grynpas and Cheng 1988 and Baud et al. 1988 for references). Fluoride has effects on both bone mineral and cellular activity (Baylink et al. 1970, Banes and Reddi 1979). For example, F ions reduce the rate of dissolution of the mineral in acidic buffers (Grynpas and Cheng 1988). Other effects on the mineral will be mentioned later. 

Gorobets BS (1968) On the luminescence of fluorapatite activated by rare-earth elements. Optics Spectr 25 154-155... 

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