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Apatite polarization

The situation with Mn + center distribution between Ca(I) and Ca(II) positions in the apatite lattice is the opposite to this for REE + in artificially activated apatite the Mn(I) center clearly dominates the fluorescence spectra (Ryan et al. 1970), while in the natural one only Mn(ll) centers have been detected (Tarashchan 1978). In order to clarify the distribution in different Ca positions, luminescence spectra have been measured with different polarizations from one section or from prismatic and basal sections with the same analytical conditions. As was foimd earher (Barbarand and Pagel 2001) the shapes of the spectra are usually the same for both crystallographic orientations, while the major difference in the spectra is their intensity, with the mean intensity for the basal section lower than for the prismatic face. Nevertheless, in certain cases polarization changes lead to different spectra (Fig. 5.46). In this case spectra are composed mainly of the Nd and Mn with relatively weak Eu lines. The polarization change results in an inversion of the relative intensities of the liuninescence bands Mn +(I) emission dominates in one orientation and REE emission is practically not seen, but Mn " (II) in other orientations is much weaker compared to Mn +(I), while the... [Pg.203]

Fig. 5.46. Polarized laser-induced luminescence of different Mn " centers in apatite... Fig. 5.46. Polarized laser-induced luminescence of different Mn " centers in apatite...
Keywords Bone Apatite Structure Solid-state NMR Cross-polarization... [Pg.235]

More information on the chemical structure of bone apatite can be obtained from H—> P CP. First, consider the dependence of peak intensity J(f) on contact time t (also denoted CT) in the conventional variable-contact time experiment (Fig. 11). Such an experiment monitors the CP kinetics, which is very specific for a particular material [12]. There are two models of the CP kinetics, I-T-S and I-S [12]. In this notation, the spin polarization is transferred from spins I to spins S, in our case from protons to P, respectively. [Pg.249]

Structural function of HPO ions in bone mineral and their content are of great biological interest. Concentration of these ions decreases as bone apatite matures with age [50,51 ]. In order to analyse scarce HPO " ions in the presence of abundant PO ions, one has to resort to a special CP technique proposed by Zumbulyadis [52] and X. Wu et al. [53], and apphed to bone mineral by Y. Wu et al. [37]. The technique is a modified version of conventional CP (Fig. 14a) and is called differential cross-polarization (DCP). The proton spin-lock is divided into two periods, f and t. During the first period, polarization is transferred, as usual, from H to P. The phase of the H spin-lock pulse is then reversed, which forces polarization to transfer backwards (depolarisation), from P to H. The DCP experiment is performed with arbitrarily chosen, constant f and constant or variable t. The variable experiment begins with CP peaks of... [Pg.254]

Solid-state C MAS NMR has been used only to study various synthetic car bonatoapatites and dental enamel [23] (Fig. 24). Chemical shifts for CO various apatite locations were determined and response of the peaks to dipolar suppression and heating was investigated. For CP, a long contact time of 10 ms was required. For BD, a recycle delay of 60 s was used. In Fig. 24, spectra A and B were recorded with and without CP. CHA-A gives a relatively sharp peak and does not cross-polarize, because COf" replaces OH , depleting the main proton source for the polarization. The spectra C and D were not adequately described in [23], so it is not sure whether BD or CP was applied. It is... [Pg.263]

In many cases inclusions in apatite can be detected during the grain selection process. At Caltech apatites to be dated are inspected at 120 x under a binocular microscope using transmitted light and crossed-polarizers. When the apatites are taken to extinction even tiny inclusions of phases like zircon stand out—in some cases entire grains appear to be shot full of inclusions. These grains are easily removed prior to analysis. In rare cases this technique has been found inadequate, usually because the inclusions are oriented parallel to the c-axis (possibly from exsolution of monazite) and are extinct at the same time as the apatite host. In these cases the re-extract test (see the Appendix) and age irreproducibility are sufficient to identify problem samples. [Pg.834]

Figure 27. Optical photomicrograph in crossed polarized transmitted light of a thin section (parallel to 001 ) through an apatite from the Asio Mine, Shimotsuke Province, Japan. Optically distinct regions correspond to different sectors and subsectors throughout the crystal. [Used by permission of the Mineralogical Society, from Akizuki et al. (1994) Mineralogical Magazine, Vol. 58, Fig. 4,p. 311.]... Figure 27. Optical photomicrograph in crossed polarized transmitted light of a thin section (parallel to 001 ) through an apatite from the Asio Mine, Shimotsuke Province, Japan. Optically distinct regions correspond to different sectors and subsectors throughout the crystal. [Used by permission of the Mineralogical Society, from Akizuki et al. (1994) Mineralogical Magazine, Vol. 58, Fig. 4,p. 311.]...
Figure 29. Optical photomicrograph of a thin section (parallel to 001 within a 100 sector) in crossed polarized transmitted hght from the same apatite crystal in Fignre 28. Optically-distinct regions correspond to the different concentric zones and snbseetors within the 100 seetor. Image is 500 pm aeross. Figure 29. Optical photomicrograph of a thin section (parallel to 001 within a 100 sector) in crossed polarized transmitted hght from the same apatite crystal in Fignre 28. Optically-distinct regions correspond to the different concentric zones and snbseetors within the 100 seetor. Image is 500 pm aeross.
Figure 30. Optical photomicrographs in crossed polarized transmitted light of an apatite in three different orientations from Huron County, Ohio, United States. The optieal path is parallel to [001]. Optically distinct regions correspond to the different 100 seetors. The crystal is 2 nun across. Figure 30. Optical photomicrographs in crossed polarized transmitted light of an apatite in three different orientations from Huron County, Ohio, United States. The optieal path is parallel to [001]. Optically distinct regions correspond to the different 100 seetors. The crystal is 2 nun across.
Fowler BO (1977) I. Polarized Raman spectra of apatites. II. Raman bands of carbonate ions in human tooth enamel. Mineralized Tissue Research Communications Vol 3, no. 68 Fratzl P, Fratzl-Zelman N, Klaushofer K, Vogl G, Roller K (1991) Nucleation and growth of mineral crystals in bone studied by small-angle X-ray scattering. Calcif Tissue Inti 48 407-413 Fratzl P, Schreiber S, Boyde A (1996) Characterization of bone mineral crystals in horse radius by small-angle X-ray scattering. Calcif Tissue Inti 58 341-346... [Pg.450]

Knowles JC, Gross K, Berndt CC, Bonfield W (1996) Stmctural changes of thermally sprayed hydroxylapatite investigated by Rietveld Analysis. Biomaterials 17 639-645 Kobayashi T, Nakamura S, Yamashita K (2001) Enhanced osteobonding by negative surface charges of electrically polarized hydroxylapatite. J Biomed Mater Res 57 477-484 Kokubo T (1998) Apatite formation on surfaces of ceramics, metals and polymers in body enviromnent. Acta Materi a 46 2519-27... [Pg.664]

UV at 248 and 278 nm, and sets of narrow bands centered at about 488 and 615 nm (Mitchell et al. 1997) yielding a brick-red emission color. Natural samples of hydroxyl-apatite and fluorapatite show similar CL bands (Gaft et al. 1999). Time-resolved emission spectra (Fig. 19) show well defined Pr emission in natural magmatic apatite at 485 and 607 nm (Gaft et al. 1999). Studies using polarized emission measurements on this sample were interpreted as representative of only Cal site occupation by Pr (Reisfeld et al. 1996). In contrast, a sedimentary apatite annealed in air showed a different Pr spectrum, with a set of bands centered at about 630 nm (Fig. 19). This spectrum was interpreted to be due to Pr in Ca2 (Reisfeld et al. 1996). Pr appears to be an efficient sensitizer for Sm, as many of its transition energies are almost identical to Sm, and in general Pr probably is more important as a sensitizer of other REE than for its own emission (Mitchell et al. 1997). [Pg.723]

Carbonate tons and Enamel. Elliott (1965) has used polarized infrared absorption spectra to study longitudinal sections of human tooth enamel in order to determine whether carbonate ions can substitute for hydroxyl ions in the enamel. His conclusion was that carbonate ions substitute to a very limited extent for hydroxyl ions. The evidence consisted of certain bands in the infrared spectra of enamel (Fig. 19.12) which coincide with those of the synthetic apatite in which this substitution is known to have taken place (Fig. 19.13). In a hydroxyapatite that had been reacted with carbon dioxide at 1000°C, carbonate ion had absorption bands at 878, 1463, and 1528cm , and the hydroxyapatite 3570 cm band (OH ) had disappeared (Fig. 19.13). Elliott examined enamel which had been heated at 1000°C in carbon dioxide and measured the dichroism of the out-of-plane deformations at the 879 cm" mode (Fig 19.14). From the dichroic ratio he was able to calculate that the plane of the carbonate ion is nearly parallel to the c-axis of the apatite. Elliott et al. (1948) have given the dichroic ratio applicable to this case as... [Pg.499]

Fig. 19.14. Polarized infrared absorption spectrum ofthe carbonate ion that has replaced hydroxyl ions in the apatite lattice. (A) A 100- i longitudinal section of enamel heated at 1100°C in air for 2 hr. (B) A 50-/t longitudinal section of enamel heated at 900 C in CO2 for 30 min. (Elliott, 1965.)... Fig. 19.14. Polarized infrared absorption spectrum ofthe carbonate ion that has replaced hydroxyl ions in the apatite lattice. (A) A 100- i longitudinal section of enamel heated at 1100°C in air for 2 hr. (B) A 50-/t longitudinal section of enamel heated at 900 C in CO2 for 30 min. (Elliott, 1965.)...
Zapanta-Le Geros et al. (1970) have recently reviewed the subject of infrared spectra of carbonate-containing synthetic and biological apatites. Klein et al. (1970) have used the polarized infrared specular-reflectance technique to study single crystals of apatites. They found this technique to be a more powerful method for the analysis of the vibration spectra of crystalline structures than the powder absorption techniques. [Pg.501]

Figure 10.26 Schematics of the accelerated growth of bone-like apatite on a negatively polarized (left column) and nonpolarized (right column) hydroxyapatite surface. Figure 10.26 Schematics of the accelerated growth of bone-like apatite on a negatively polarized (left column) and nonpolarized (right column) hydroxyapatite surface.
Fukada and co-workers [510,317-519,522] observed pyroelectricity and piezoelectricity in various kinds of uniaxially oriented biopolymers. Lang [521] also reported pyroeleciricily of bone and tendon. The electrical stimulation of repair and growth (rf bone has attracted a great deal of interest in the field of orthopedics. Pyro- and piezoelectric studies in various types of biological systems showed the presence of natural polarity in the structure of various parts of animals and plants [520]. Bennis ct al. [511] have shown that TSC technique is particularly adaptable for studying the characteristics of bioelectrets of apatites and similar biological materials. [Pg.45]

The two main problems concern the reactivity between the MIEC and the solid electrolyte and the appearance of electronic conductivity in the sohd electrolyte inducing polarization phenomena. The appropriate choice of the solid electrolyte can noticeably reduce the chemical reactivity as an example, ceiia-based electrolyte or apatite is less reactive than stabilized zirconia [Mauvy et al., 2009]. Double-electrolyte cells have been proposed to extend the oxygen activity range of thermodynamic cell measurements compared to the range of a single-electrolyte cell arrangement [Shores Rapp, 1971 Tretyakov Muan, 1969],... [Pg.186]


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