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Ren, Fu Zeng y Yang Leng. "Carbonated Apatite, Type-A or Type-B?" Key Engineering Materials 493-494 (octubre de 2011): 293–97. http://dx.doi.org/10.4028/www.scientific.net/kem.493-494.293.
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Carbonated apatite, the basic mineral component in human hard tissues and an important bioceramic material, has been extensively studied. However, its atomic arrangements in apatite crystal structure and its experimental characterization are still not lack of debating. We analyzed infrared (IR) vibrational spectroscopy for carbonated apatite determinations, by comparatively studying the IR spectra of hydroxyapatite and of surface carbonate absorption, biological apatites (human enamel, human cortical bone, and two animal bones) and carbonated apatite. The carbonated apatite samples were sythesized by various methods, including precipitation method, hydrothermal reaction and solid-gas reaction at high temperature. The comparative study indicates that the bands at ~880 cm-1, ~1413 cm-1, and ~1450 cm-1 should not be used to identify carbonated apatite since they may result from carbonate absorption on surfaces of apatite crystals or separated carbonate phase present with apatite crystals. The IR characteristic bands of carbonate substitution in apatites should be: ν3 at ~1465 cm-1 for type-B (CO3 substituting for PO4) and ν3 band at ~1546 cm-1 for type A (CO3 substituting for OH). These signature IR bands are further confirmed by the ab initio simulations.
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Hong, S. I., K. H. Lee, M. E. Outslay y D. H. Kohn. "Ultrastructural analyses of nanoscale apatite biomimetically grown on organic template". Journal of Materials Research 23, n.º 2 (febrero de 2008): 478–85. http://dx.doi.org/10.1557/jmr.2008.0051.
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The ultrastructure of nanoscale apatite biomimetically formed on an organic template from a supersaturated mineralizing solution was studied to examine the morphological and crystalline arrangement of mineral apatites. Needle-shaped apatite crystal plates with a size distribution of ∼100 to ∼1000 nm and the long axis parallel to the c axis ([002]) were randomly distributed in the mineral films. Between these randomly distributed needle-shaped apatite crystals, amorphous phases and apatite crystals (∼20–40 nm) with the normal of the grains quasi-perpendicular to the c axis were observed. These observations suggest that the apatite film is an interwoven structure of amorphous phases and apatite crystals with various orientations. The mechanisms underlying the shape of the crystalline apatite plate and aggregated apatite nodules are discussed from an energy-barrier point of view. The plate or needle-shaped apatite is favored in single-crystalline form, whereas the granular nodules are favored in the polycrystalline apatite aggregate. The similarity in shape in both single-crystalline needle-shaped apatite and polycrystalline granular apatite over a wide range of sizes is explained by the principle of similitude, in which the growth and shape are determined by the forces acting upon the surface area and the volume.
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Shimoda, S., T. Aoba, E. C. Moreno y Y. Miake. "Effect of Solution Composition on Morphological and Structural Features of Carbonated Calcium Apatites". Journal of Dental Research 69, n.º 11 (noviembre de 1990): 1731–40. http://dx.doi.org/10.1177/00220345900690110501.
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The composition of enamel mineral corresponds to that of a calcium carbonato-apatite. For insight to be gained into the precipitation of carbonato-apatites having specific properties (crystal size, morphology, and carbonate incorporation into the crystal lattice), apatites were prepared at 80°C in aqueous systems having various CO3 concentrations and pH values of around 7.5 or 10.5 (± 0.5). The various preparations had a wide range (0.005 to 0.19) of CO3/Ca molar ratios that bracket the ratios found in porcine enamel mineral at various developmental stages. Fourier transform infrared spectroscopy (FTIR) and x-ray diffraction analyses showed that the calcium apatites precipitating at neutral pH incorporated the carbonate into both the hydroxyl and phosphate ion sites in their lattices (A,B-types), whereas the preparations made at the alkaline pH (high OH-CO32- competition) or in the presence of fluoride (F--CO32- competition) yielded only the B-type carbonato-apatite. It was also ascertained that the size and morphology of the carbonato-apatites, assessed by specific surface area determination and high-resolution electron microscopy, were highly dependent on the driving force for precipitation and the presence of regulators (CO 32- and F-) in solution. In neutral media, early precipitates were thin-ribbon in appearance, but grew into crystals having flattened-hexagonal cross-sections. In the presence of fluoride or in alkaline media, acicular apatite crystals, precipitated initially, grew into large rod-like carbonato-apatites having a symmetric-hexagonal cross-section. In both neutral and alkaline solutions, carbonate inhibited the growth of apatite crystals along their c axis, leading to the formation of bulkier crystals. The formation of carbonato-apatites at the neutral pH and their properties are consistent with observations made on enamel minerals formed in the early developmental stages.
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Ishikawa, K., E. D. Eanes y M. S. Tung. "The Effect of Supersaturation on Apatite Crystal Formation in Aqueous Solutions at Physiologic pH and Temperature". Journal of Dental Research 73, n.º 8 (agosto de 1994): 1462–69. http://dx.doi.org/10.1177/00220345940730081101.
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The importance of supersaturation in the dynamics of apatite precipitation from aqueous solutions is well-established. To determine whether this parameter has a comparable impact on the concomitant development of the textural properties of this phase, such as crystal size and shape, we investigated mineral accretion in synthetic solutions seeded with 0.67 g/L apatite over a range of supersaturations at pH 7.4 and 37°C. A dual specific-ion electrode-controlled titration method was used to maintain the seeded reactions under the following solution conditions: 1.0 to 1.8 mmol/L Ca2+, 0.67 to 1.2 mmol/L total phosphate (PO 4), Ca/PO4 (initial) = 1.5, 143 mmol/L KNO3, and 10 mmol/L HEPES. Samples were collected for chemical and textural analyses when the seed apatite was reduced by new accretions to 1/2,1/4,1/8,1/16, and 1/32 of the total solids in suspension. All new accretions were found to be apatitic. At the lowest supersaturation, accretion occurred primarily by growth of the seed crystals. However, at the highest supersaturation examined, the crystals at the end of the experiments were actually smaller, on average, than the original seeds, even though the total mass increased 32-fold. The results suggest that proliferation of new crystals supplanted growth of the seed crystals as supersaturation was increased. The results also suggest that differences in tissue fluid supersaturation may contribute to the large disparity in dimensions between dentin and enamel apatite crystals.
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PARK, JONGEE y ABDULLAH OZTURK. "BIOACTIVITY OF APATITE–WOLLASTONITE GLASS-CERAMICS PRODUCED BY MELTING CASTING". Surface Review and Letters 20, n.º 01 (febrero de 2013): 1350010. http://dx.doi.org/10.1142/s0218625x13500108.
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Glass-ceramics containing only apatite and wollastonite crystals were produced in the system MgO-CaO-SiO2-P2O5-F by the melt casting process. The bioactivity of the glass-ceramics was determined by immersing the glass-ceramics in a simulated body fluid (SBF) and by assessing the resulting apatite formation on the free surface after various immersion durations. A 12-μm-thick apatite layer formed on the surface of the glass-ceramic containing only apatite crystals after 20 days immersion in SBF. However, the thickness of the apatite layer formed on the surface of the glass-ceramic containing apatite and wollastonite crystals was 1 μm. Results have shown that the bioactivity of glass-ceramic depends strongly on the type of crystal(s) developed during the glass-ceramic process and their proportion in the glassy matrix.
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Shevchyk, A. O., I. G. Svidrak, N. T. Bilyk y I. V. Poberezhska. "Crystallomorphological and physical properties of apatite from carbonatites". Scientific Messenger of LNU of Veterinary Medicine and Biotechnologies 23, n.º 95 (9 de abril de 2021): 25–32. http://dx.doi.org/10.32718/nvlvet-f9505.
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This paper presents the results of the study of x-ray luminescence of apatite from different genetic types of apatite species in order to study its geochemical characteristics and the possibility of using as a mineral indicator the conditions of ore formation and for search purposes. Apatite Ca2Ca3(F,Cl,OH)2[PO4]3 contains impurities Gd3+, Ce3+, Eu2+, Dy3+, Sm3+, Nd3+ as well as Mn2+ and others. Syngony is hexagonal. Crystals of prismatic habit; usually ending in dipyramide or basopinacoid. Sometimes forms tabular crystals. A hexagonal prism is often preserved. Color greenish, bluish-green; pinkish-purple, gray; often white, colorless or brown. Quite often translucent due to the presence of small internal cracks and inclusions; sometimes the inclusions are arranged oriented, preferably parallel to the main axis of the crystal. Brightly luminesces in cathode, x-ray and ultraviolet rays. The intensity and color of luminescence varies widely depending on the impurities. The presence of three crystal chemical positions in the structure of apatite – two cationic and one anionic makes it possible to be realized in the mineral by a wide heterovalent substitution. The distribution of isomorphic impurities between the crystal chemical positions will depend on the type of cation, its amount, as well as anionic substitutions in apatite. To determine the luminescence intensity values of the characteristic isomorphic impurities of apatite TR3+ (Gd3+, Ce3+, Eu2+, Dy3+, Sm3+, Nd3+) and Mn2+, the X-ray luminescence method was applied. Apatites of different genetic types of the Aldan, Baltic Shields, the Baikal region (Russia), the Sette-Daban Range, and the Maimech-Kotui Province (Yakutia) and the Ukrainian Shield were investigated. The obtained values of luminescence intensity of TR3+ and Mn2+ can be used to diagnose the genetic type of apatite species, the conditions of mineral formation, the type of their mineralization and for search purposes. On the basis of factor analysis, it can be concluded that the intensity of the luminescence centers of rare earth elements in the apatites of each complex depends on the relative age position of the mineral in the groups of successively formed rocks. Analysis of apatite carbonatites from different deposits showed minimal fluctuations in the ratios of radiation intensity of X-ray centers (Ce3+, Sm3+, Mn2+, Eu2+), which may indicate a close geochemical situation and, consequently, the only source of matter in the formation of carbonates. Analysis of apatite carbonatites from different fields showed minimal fluctuations in the radiation intensity ratios of the centers of X-ray luminescence (Ce3+, Sm3+, Mn2+, Eu2+), which, in my opinion, may indicate a close geochemical situation and, as a consequence, the substance or the result.
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Simmelink, J. W. y S. C. Abrigo. "Crystal Morphology and Decalcification Patterns Compared in Rat and Human Enamel and Synthetic Hydroxyapatite". Advances in Dental Research 3, n.º 2 (septiembre de 1989): 241–48. http://dx.doi.org/10.1177/08959374890030022501.
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The purpose of this investigation was to compare morphology and dissolution patterns by ultrastructural examination of rat and human enamel crystals as well as synthetic apatite crystals. Mature enamel crystals were of particular interest, since crystal maturation appears to be inhibited in amelogenesis imperfecta. Specimens were isolated from developing and mature rat incisor enamel. Rat enamel, mature human enamel, and synthetic apatite were thin-sectioned without decalcification and examined by transmission electron microscopy. Some sections were exposed to acid, and selected synthetic apatite sections were further treated for removal of embedding plastic, followed by vacuum-shadow-coating with carbon. Results showed that cross-sections of rat, human, and synthetic crystals had a distortion in the flattened hexagonal outline in regions where the growth of one crystal impinged on another. Crystal dissolution occurred preferentially along the c-axis, producing a central defect or hole in the crystals. Preliminary studies with weak acid on mature human enamel indicate that the relatively soluble crystal core is quickly dissolved, while the outer shell remains intact over a much longer period of time. In the mature rat and human enamel, this crystal hole formation had a consistent dimension of approximately 10-nm thickness. The crystal hole dimension was the same size as crystals that are formed during the early secretory phase in rat amelogenesis. Acid-treated synthetic apatite also showed dissolution of the crystal core along the c-axis, but dimensions of the hole were not consistent. Shadowed grids showed that the defective hole penetrated the entire section thickness. Mature human enamel showed a unique variation to acid at rod borders where larger, isohexagonal crystals were resistant to acid dissolution. It was concluded that (1) crystals of rat and human enamel show evidence of diphasic growth that may affect their dissolution properties, and (2) unique acid-resistant crystals in human enamel at rod borders may be a result of long oral exposure.
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Deng, Chun Lin, Ying Jun Wang, Yao Wu, Xin Long Wang, Xiao Feng Chen, Hua De Zheng, Ji Yong Chen y Xing Dong Zhang. "Apatite Formation on Porous HA/TCP in Animals’ Serums In Vitro". Key Engineering Materials 330-332 (febrero de 2007): 955–58. http://dx.doi.org/10.4028/www.scientific.net/kem.330-332.955.
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Porous HA/TCP bioceramics were immersed in pure dog serum to observe apatite formation. Deposited crystals were examined using SEM. Results showed that beamed sheet-like crystals formed on the surface of ceramics granules, and after postponement immersion time, crystals extended and became bigger. EDS and IR results suggested formed crystals were defect-calcium type carbonated hydroxyapatite. HRTEM photograph suggested formation process of new-formed crystals from non-crystal to crystal in serum. Directional organisms acted maybe as a template in process of crystals formation, so new crystals developed along certain direction.
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Rey, Christian, Christèle Combes, Christophe Drouet y Hocine Sfihi. "Chemical Diversity of Apatites". Advances in Science and Technology 49 (octubre de 2006): 27–36. http://dx.doi.org/10.4028/www.scientific.net/ast.49.27.
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Apatites can accommodate a large number of vacancies and afford multiple ionic substitutions determining their reactivity and biological properties. Unlike other biominerals they offer a unique adaptability to various biological functions. The diversity of apatites is essentially related to their structure and to their mode of formation. Special charge compensation mechanisms allow molecular insertions and ion substitutions and determine to some extent their solubility behaviour. Apatite formation at physiological pH involves a structured surface hydrated layer nourishing the development of apatite domains. This surface layer contains relatively mobile and exchangeable ions, and is mainly responsible for the surface properties of apatite crystals from a chemical (dissolution properties, ion exchange ability, ion insertions, molecule adsorption and insertions) and a physical (surface charge, interfacial energy) point of view. These characteristics are used by living organisms and can also be exploited in material science.
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Mészárosová, Noemi, Roman Skála, Šárka Matoušková, Petr Mikysek, Jakub Plášil y Ivana Císařová. "Hydrothermal-to-metasomatic overprint of the neovolcanic rocks evidenced by composite apatite crystals: a case study from the Maglovec Hill, Slanské vrchy Mountains, Slovakia". Geologica Carpathica 69, n.º 5 (1 de octubre de 2018): 439–52. http://dx.doi.org/10.1515/geoca-2018-0025.
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Abstract The apatite assemblage from Maglovec hill (Slanské vrchy Mountains near the city of Prešov) from fissures of hydrothermally altered neovolcanic rocks (andesites and related lithologies) was studied. The assemblage consists of two different morphological apatite types (apatite in cores of prismatic crystals and fibrous apatite mantling these cores). The assemblage was investigated by a multi-analytical approach to reveal its unique chemical composition and structure. Both types of apatite display zoning visible in back-scattered electron (BSE) images. Core apatite is relatively homogenous with porous rims appearing darker in the BSE images at the contact with fibrous apatite, and occasionally with darker regions along fractures. These parts are depleted in trace elements, mostly in LREE. Fibrous apatites display concentric and/or patchy zoning. Dark regions in fibrous apatite occasionally display a porous structure. In part of fibrous crystals, substitution of (CO3)2− for phosphorus is confirmed by Raman spectroscopy by the presence of a band at ~ 1071 cm−1. This method also confirmed the presence of OH in different populations in the structure of all apatite types. The three most important observed peaks are caused by vibrations of hydroxyls influenced by different adjacent anions: hydroxyl (band at ~ 3575 cm−1); fluorine (band at ~ 3535–3540 cm−1); chlorine (band at ~ 3494 cm−1). In REE-depleted parts of both apatite types, fine inclusions of monazite and rarely Th-rich silicate are observed. The acquired data suggest a hydrothermal origin of this assemblage and indicate a formation sequence of distinct apatite types. Moreover, minerals from the epidote group were identified, which have not been described from this locality before as well as vanadium-rich magnetites that form exsolution lamellae in ilmenite grains.
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Roveri, Norberto, Elisa Battistella, Claudia Letizia Bianchi, Ismaela Foltran, Elisabetta Foresti, Michele Iafisco, Marco Lelli, Alberto Naldoni, Barbara Palazzo y Lia Rimondini. "Surface Enamel Remineralization: Biomimetic Apatite Nanocrystals and Fluoride Ions Different Effects". Journal of Nanomaterials 2009 (2009): 1–9. http://dx.doi.org/10.1155/2009/746383.
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A new method for altered enamel surface remineralization has been proposed. To this aim carbonate-hydroxyapatite nanocrystals which mimic for composition, structure, nanodimensions, and morphology dentine apatite crystals and resemble closely natural apatite chemical-physical properties have been used. The results underline the differences induced by the use of fluoride ions and hydroxyapatite nanocrystals in contrasting the mechanical abrasions and acid attacks to which tooth enamel is exposed. Fluoride ions generate a surface modification of the natural enamel apatite crystals increasing their crystallinity degree and relative mechanical and acid resistance. On the other hand, the remineralization produced by carbonate-hydroxyapatite consists in a deposition of a new apatitic mineral into the eroded enamel surface scratches. A new biomimetic mineral coating, which progressively fills and shadows surface scratches, covers and safeguards the enamel structure by contrasting the acid and bacteria attacks.
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Barbarand, Jocelyn y Maurice Pagel. "Cathodoluminescence study of apatite crystals". American Mineralogist 86, n.º 4 (abril de 2001): 473–84. http://dx.doi.org/10.2138/am-2001-0411.
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Aoba, T. "Strategies for Improving the Assessment of Dental Fluorosis: Focus on Chemical and Biochemical Aspects". Advances in Dental Research 8, n.º 1 (junio de 1994): 66–74. http://dx.doi.org/10.1177/08959374940080011201.
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In order to assess fluoride accumulation and effects in developing dental tissues, one must determine the concentration profile of fluoride in the tissue and to assess separately the labile (i.e., free ions in fluid and ions associated with organic matter) and stable (i.e., incorporated into apatite lattice) pools of fluoride. Free fluoride ions in the mineralizing milieu markedly affect the driving force for precipitation and, as a result, the nature of precipitating crystals. The fluoride incorporated into the crystalline lattice increases the stability of the formed mineral. Improvement in the understanding of the mechanism of dental fluorosis requires more comprehensive information about the effects of fluoride on the ionic composition of the fluid phase, the nature of the initially precipitating mineral(s), the interactions between crystals and matrix proteins, and the enzymatic degradation of the proteins. Recent observations relevant to the role of fluoride in enamel formation include: (1) that there are threshold concentrations of fluoride below which the precipitation and hydrolysis of thin-platy octacalcium phosphate is facilitated but beyond which de novo apatite precipitation prevails; (2) that the presence of fluoride in the mineralizing milieu most likely affects the steady-state concentrations of mineral lattice ions; (3) that incorporation of fluoride into the stable pool is retarded by the presence of matrix proteins, particularly amelogenins, which inhibit the growth of apatite crystals; (4) that increasing the degree of fluoridation of apatite crystals enhances the adsorption of amelogenins onto the crystal surface, and (5) that amelogenins pre-adsorbed onto apatite crystals are more resistant to enzymatic cleavages by trypsin (used as a prototype of amelogeninases).
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Li, Xiyu, Qin Zou, Haifeng Chen y Wei Li. "In vivo changes of nanoapatite crystals during bone reconstruction and the differences with native bone apatite". Science Advances 5, n.º 11 (noviembre de 2019): eaay6484. http://dx.doi.org/10.1126/sciadv.aay6484.
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Hydroxyapatite (HA) plays an important role in clinical bone repair. However, it remains a challenge to accurately determine its changes during bone reconstruction and to identify its differences from native bone apatite. Here, terbium (Tb) doped uniform HA nanocrystals were implanted into bone tissue and compared with native bone apatite. These comparisons demonstrated the occurrence of compositional and structural alteration of the implanted HA nanocrystals, and their gradual degradation, during bone reconstruction. They also revealed notable differences between HA nanocrystals and bone apatite crystals in crystal size, distribution pattern, and state of existence in bone tissue. Although synthetic HA nanocrystals could osteointegrate with bone tissue, they still seemed to be treated as foreign material in this tissue and thus were gradually degraded. These findings can help to identify and rethink the function of synthetic apatite and bone apatite, which will benefit future design and application of biomimetic bone repair materials.
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Roveri, Norberto, Elisa Battistella, Ismaela Foltran, Elisabetta Foresti, Michele Iafisco, Marco Lelli, Barbara Palazzo y Lia Rimondini. "Synthetic Biomimetic Carbonate-Hydroxyapatite Nanocrystals for Enamel Remineralization". Advanced Materials Research 47-50 (junio de 2008): 821–24. http://dx.doi.org/10.4028/www.scientific.net/amr.47-50.821.
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New biomimetic carbonate-hydroxyapatite nanocrystals (CHA) have been designed and synthesized in order to obtain a remineralization of the altered enamel surfaces. Synthesized CHA mimic for composition, structure, nano dimension and morphology bone apatite crystals and their chemical-physical properties resemble closely those exhibited by enamel natural apatite. CHA can chemically bound themselves on the surface of natural enamel apatite thanks to their tailored biomimetic characteristics. The remineralization effect induced by CHA represents a real new deposition of carbonate-hydroxyapatite into the eroded enamel surface scratches forming a persistent biomimetic mineral coating, which covers and safeguards the enamel structure. The experimental results point out the possibility to use materials alternative to fluoride compounds which is commonly utilized to contrast the mechanical abrasions and acid attacks. The apatitic synthetic coating is less crystalline than enamel natural apatite, but consists of a new biomimetic apatitic mineral deposition which progressively fills the surface scratches. Therefore the application of biomimetic CHA may be considered an innovative approach to contrast the acid and bacteria attacks.
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Ravenhurst, Casey E., Mary K. Roden-Tice y Donald S. Miller. "Thermal annealing of fission tracks in fluorapatite, chlorapatite, manganoanapatite, and Durango apatite: experimental results". Canadian Journal of Earth Sciences 40, n.º 7 (1 de julio de 2003): 995–1007. http://dx.doi.org/10.1139/e03-032.
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It is well known that the optically measured lengths of fission tracks in apatite crystals are a function of etching conditions, crystallographic orientation of the track, composition of the crystal, and the state of thermal annealing. In this study we standardize etching conditions and optimize track length measurability by etching until etch pits formed at the surface of each apatite crystal reached widths of about 0.74 μm. Etching times using 5M HNO3 at 21°C were 31 s for Otter Lake, Quebec, fluorapatite; 47 s for Durango, Mexico, apatite; 33 s for Portland, Connecticut, manganoanapatite; and 11 s for Bamle, Norway, chlorapatite. An etching experiment using two etchant strengths (5M and 1.6M HNO3) revealed that, despite significant differences in etch pit shape, fission-track length anisotropy with respect to crystallographic orientation of the tracks is not a chemical etching effect. A series of 227 constant-temperature annealing experiments were carried out on nuclear reactor induced tracks in oriented slices of the apatites. After etching, crystallographic orientations of tracks were measured along with their lengths. The 200300 track lengths measured for each slice were ellipse-fitted to give the major (c crystallographic direction) and minor (a crystallographic direction) semi-axes used to calculate equivalent isotropic lengths. The equivalent isotropic length is more useful than mean length for thermal history analysis because the variation caused by anisotropy has been removed. Using normalized etching procedures and equivalent isotropic length data, we found that the fluorapatite anneals most readily, followed by Durango apatite, manganoanapatite, and lastly chlorapatite.
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Mitchell, Roger H., Rudy Wahl y Anthony Cohen. "Mineralogy and genesis of pyrochlore apatitite from The Good Hope Carbonatite, Ontario: A potential niobium deposit". Mineralogical Magazine 84, n.º 1 (4 de octubre de 2019): 81–91. http://dx.doi.org/10.1180/mgm.2019.64.
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AbstractThe Good Hope carbonatite is located adjacent to the Prairie Lake alkaline rock and carbonatite complex in northwestern Ontario. The occurrence is a heterolithic breccia consisting of diverse calcite, dolomite and ferrodolomite carbonatites containing clasts of magnesio-arfvedsonite + potassium feldspar, phlogopite + potassium feldspar together with pyrochlore-bearing apatitite clasts. The apatitite occurs as angular, boudinaged and schlieren clasts up to 5 cm in maximum dimensions. In these pyrochlore occurs principally as euhedral single crystals (0.1–1.5 cm) and can comprise up to 25 vol.% of the clasts. Individual clasts contain compositionally- and texturally-distinct suites of pyrochlore. The pyrochlores are hosted by small prismatic crystals of apatite (~100–500 μm × 10–25 μm) that are commonly flow-aligned and in some instances occur as folds. Allotriogranular cumulate textures are not evident in the apatitites. The fluorapatite does not exhibit compositional zonation under back-scattered electron spectroscopy, although ultraviolet and cathodoluminescence imagery shows distinct cores with thin (<50 μm) overgrowths. Apatite lacks fluid or solid inclusions of other minerals. The apatite is rich in Sr (7030–13,000 ppm) and rare earth elements and exhibits depletions in La, Ce, Pr and Nd (La/NdCN ratios (0.73–1.14) relative to apatite in cumulate apatitites (La/NdCN > 1.5) in the adjacent Prairie Lake complex. The pyrochlore are primarily Na–Ca pyrochlore of relatively uniform composition and minor Sr contents (<2 wt.% SrO). Irregular resorbed cores of some pyrochlores are A-site deficient (>50%) and enriched in Sr (6–10 wt.% SrO), BaO (0.5–3.5 wt.%), Ta2O5 (1–2 wt.%) and UO2 (0.5–2 wt.%). Many of the pyrochlores exhibit oscillatory zoning. Experimental data on the phase relationships of haplocarbonatite melts predicts the formation of apatite and pyrochlore as the initial liquidus phases in such systems. However, the texture of the clasts indicates that pyrochlore and apatite did not crystallise together and it is concluded that pyrochlores formed in one magma have been mechanically mixed with a different apatite-rich magma. Segregation of the apatite–pyrochlore assemblage followed by lithification resulted in the apatitites, which were disrupted and fragmented by subsequent batches of diverse carbonatites. The genesis of the pyrochlore apatitites is considered to be a process of magma mixing and not simple in situ crystallisation.
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Oyane, Ayako, Masaki Uchida, Yousuke Ishihara y Atsuo Ito. "Ultra-Structural Study of the Laminin-Apatite Composite Layer Formed on Ethylene-Vinyl Alcohol Copolymer by a Biomimetic Process". Key Engineering Materials 284-286 (abril de 2005): 227–30. http://dx.doi.org/10.4028/www.scientific.net/kem.284-286.227.
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Mechanism of formation of a laminin-apatite composite layer on the surface of an ethylene-vinyl alcohol copolymer (EVOH) using a liquid phase coating process was investigated by transmission electron microscopy (TEM). In this coating process, an EVOH substrate is alternately dipped in calcium and phosphate solutions, and then immersed in a laminin-containing calcium phosphate (LCP) solution. From the results obtained by the present study, formation of the laminin-apatite composite layer on EVOH is likely to proceed via the following events. By the alternate dipping process, particulate amorphous calcium phosphate, which is a precursor of apatite, was deposited onto the EVOH surface. When the specimen was subsequently immersed in the LCP solution, the amorphous calcium phosphate on the specimen transformed itself into needle-like apatite crystal, and then grew into a layer. During this process, laminin molecules contained in the LCP solution were incorporated into a matrix of the apatite crystals to produce a laminin-apatite composite layer on the EVOH surface.
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Dorozhkin, Sergey V. "A hierarchical structure for apatite crystals". Journal of Materials Science: Materials in Medicine 18, n.º 2 (febrero de 2007): 363–66. http://dx.doi.org/10.1007/s10856-006-0701-x.
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Bodył, Sabina. "Luminescence properties of Ce3+ and Eu2+ in fluorites and apatites". Mineralogia 40, n.º 1-4 (1 de enero de 2009): 85–94. http://dx.doi.org/10.2478/v10002-009-0007-y.
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Luminescence properties of Ce3+ and Eu2+ in fluorites and apatitesNatural samples of fluorite and apatite from granites, pegmatites, carbonatites and andesitic tuffs were investigated by steady-time spectroscopy to characterize the luminescence properties of Ce3+ and Eu2+. The luminescence of Ce3+ has been clearly seen in fluorite as 320 and 337 or 343 nm bands. In apatites, two distinct bands for two different Ca crystal sites were obtained: 340-380 nm for Ca(1) and 420-450 nm for Ca(2). The luminescence spectra of Eu2+ in the fluorite crystals were measured even at for low concentration of this element (0.11 ppm). For Ce3+, it has been showed that the crystal field strength depends more on the nature of the ligand than on the Me-ligand distances.
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Habelitz, S., A. Kullar, S. J. Marshall, P. K. DenBesten, M. Balooch, G. W. Marshall y W. Li. "Amelogenin-guided Crystal Growth on Fluoroapatite Glass-ceramics". Journal of Dental Research 83, n.º 9 (septiembre de 2004): 698–702. http://dx.doi.org/10.1177/154405910408300908.
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The formation of aligned fibrous apatite crystals in enamel is predominantly attributed to the involvement of amelogenin proteins. We developed a model to study interactions of matrix proteins with apatite mineral in vitro and tested the hypothesis that amelogenin solubility affects the ability to induce protein-guided mineralization. Crystal growth experiments were performed on fluoroapatite (FAP) glass-ceramics in mineralizing solutions containing recombinant full-length amelogenin (rH174) at different concentrations. Using atomic force microscopy, we observed that mineral precipitated randomly on the substrate, but also formed thin layers (height, 10 nm) on FAP within 24 hrs. This growth pattern was unaffected when 0.4 mg/mL of rH174 was added. In contrast, crystals grew on FAP at a rate up to 20 times higher, at 1.6 mg/mL protein. Furthermore, nanospheres and mineral bound specifically to FAP and aligned in strings approximately parallel to the c-axis of FAP, leading us to the conclusion that amelogenin proteins indeed control direction and rate of growth of apatite in enamel.
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García-Tuñón, Esther, Bruno Dacuña, Guillermo Zaragoza, Jaime Franco y Francisco Guitián. "Cl–OH ion-exchanging process in chlorapatite (Ca5(PO4)3Cl x (OH)1 − x ) – a deep insight". Acta Crystallographica Section B Structural Science 68, n.º 5 (13 de septiembre de 2012): 467–79. http://dx.doi.org/10.1107/s0108768112019520.
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We have synthesized large chlorapatite [ClAp, Ca5(PO4)3Cl x (OH)1 − x , where x = 1] single crystals using the molten salt method. We have corroborated that the hexagonal symmetry P63/m describes the crystal structure best, even though the crystals are synthetic and stoichiometric. Moreover, we have performed several thermal treatments on these ClAp crystals, generating new single crystals in the apatite system [Ca5(PO4)3Cl x (OH)1 − x , where x ≤ 1], where the chloride anions (Cl−) were systematically substituted by hydroxyl anions (OH−). These new single crystals were methodically characterized by powder and single-crystal X-ray diffraction (SXRD), scanning electron microscopy (SEM), Fourier transform–IR spectroscopy (FT–IR), and energy-dispersive X-ray spectroscopy (EDS). We have discovered a previously unreported OH− inclusion site substituting the Cl− anion during the ion-exchanging process. Finally, we evaluated the atomic rearrangements of the other species involved in the structure. These movements are associated with ionic exchange, which can be justified from an energetic point of view. We also found a novel phase transformation at high temperature. When the crystals are heated over 1753 K the apatite system evolves to a less ordered monoclinic structure, in which the complete loss of the species in the anionic channel (Cl−, OH−) has been confirmed.
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Kontonasaki, Eleana, Nikolaos Kantiranis, Xanthippi Chatzistavrou, Lambrini Papadopoulou, Konstantinos M. Paraskevopoulos y Petros Koidis. "Studying Dental Ceramic-Bioactive Glass Composites". Key Engineering Materials 361-363 (noviembre de 2007): 881–84. http://dx.doi.org/10.4028/www.scientific.net/kem.361-363.881.
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Dental ceramic-bioactive glass composites support the attachment and proliferation of human periodontal ligament cells, while their immersion in a simulated body fluid (SBF) results in the precipitation of biological hydroxyapatite further supporting cell proliferation [1]. The aim of the present study was the comparative evaluation of three dental ceramic-bioactive glass composites’ crystal structure relative to bioactive glass amount and the evaluation of their bioactivity. All composites consisted of leucite and Na2CaSi3O9 crystals dispersed in amorphous glassy matrix. Leucite and Na2CaSi3O9 crystals decreased significantly in all composites with the highest amount of dental ceramic, which did not precipitated apatite during the examined immersion time in SBF. An increase of Na2CaSi3O9 crystals in the composites with the highest amount of bioactive glass resulted in faster apatite formation. Increased bioactivity was linearly correlated to increased amount of bioactive glass.
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Akizuki, Mizuhiko, Hirotugu Nisidoh, Yasuhiro Kudoh, Tomohiro Watanabe y Kazuo Kurata. "Sector growth and symmetry of (F,OH) apatite from the Asio mine, Japan". Mineralogical Magazine 58, n.º 391 (junio de 1994): 307–14. http://dx.doi.org/10.1180/minmag.1994.058.391.13.
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AbstractA study of apatite crystals from the Asio mine, Japan, showed sectoral texture related to the growth of the crystal, and with optically biaxial properties within the sectors. Wet chemical analysis gave a composition Ca5(PO4)3(F0.64,OH0.38,Cl0.01)1.03 for the specimen.Additional diffraction spots were not observed in precession and oscillation X-ray photographs and electron diffraction photographs. Since the internal textures correlate with the surface growth features, it is suggested that the internal textures and the unusual optical properties were produced during nonequilibrium crystal growth. The fluorine/hydroxyl sites in hexagonal apatite are symmetrically equivalent in the solid crystal but, at a growth surface, this equivalence may be lost, resulting in a reduction of crystal symmetry. Heating of the apatite to about 850°C results in the almost complete disappearance of the optical anomalies due to disordering, which may be related to the loss of hydroxyl from the crystal.
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Mordberg, L. E., C. J. Stanley y A. V. Antonov. "Polystage apatite recrystallization and svanbergite formation during weathering in an acid karstic environment". Mineralogical Magazine 72, n.º 1 (febrero de 2008): 95–99. http://dx.doi.org/10.1180/minmag.2008.072.1.95.
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AbstractA Devonian weathering profile was developed near the contact of Riphean dolostone containing disseminated carbonate-fluorapatite and intensively pyritized black shales. Samples from the profile were investigated by XRF, SEM, electron microprobe and ion microprobe. Rock-forming minerals are apatite, diaspore, chlorite and kaolinite, while accessory minerals are svanbergite, anatase, pyrite and zircon.Primary marine carbonate-fluorapatite is represented by extremely weathered crystals concentrated near the footwall. Dissolution of apatite and pyrite provided an acidic environment that is expressed in the formation of S-rich apatite and svanbergite. The environment allowed Ti migration which formed anatase in weathered apatite grains. Coupled substitution Na+ + S6+ = Ca2+ + P5+ is suggested in S-rich apatite. A large volume of dissolved carbonate rocks was a source of Sr necessary for svanbergite formation. Apatite of the third generation formed at the final stage of weathering is represented by small (10—30 μm) very well shaped crystals.
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Rhee, Sang Hoon, Yong Keun Lee y Bum Soon Lim. "Effect of Silica Content in the PMMA/Silica Nano-Composite on the Mechanical Properties and Growth Behavior of Calcium Phosphate Crystals during Cell Culture". Key Engineering Materials 284-286 (abril de 2005): 165–68. http://dx.doi.org/10.4028/www.scientific.net/kem.284-286.165.
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The effect of silica content in the PMMA/silica nano-composite on the mechanical properties and the growth behavior of apatite crystals were investigated. The PMMA/silica nano-composites with different silica content were synthesized through the sol-gel reaction with triethoxysilane end-capped PMMA and tetraethyl orthosilicate (TEOS). The compressive strength showed its maximum value when the content of TEOS was 20 wt% while the elastic modulus showed its maximum value when the content of TEOS was 60 wt%. The growth behavior of the apatite crystals following the cell culture showed different response according to the silica content. As increasing the TEOS content, the shape of the apatite crystals changed from globule-like structure to fiber-like one.
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Klüver, E. y Hk Müller-Buschbaum. "Über einen Lanthanoid-Mangan-Apatit: Nd4Mn(SiO4)3O / On a Lanthanoid Manganese Apatite: Nd4Mn(SiO4)3O". Zeitschrift für Naturforschung B 50, n.º 1 (1 de enero de 1995): 61–65. http://dx.doi.org/10.1515/znb-1995-0112.
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Single crystals of Nd4Mn(SiO4)3O have been prepared by a Bi2O3 flux in closed copper tubes. The colourless crystals show hexagonal symmetry, space group C6h2—P63/m, a = 9,4986(9), c = 6,944(2) Å, Z = 2. Nd4Mn(SiO4)3O crystallizes in the Apatite structure and shows Nd3+ and Mn2+ with partly statistical distribution. As a consequence of this, O(2) and O(4) are occupying split positions.
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Treloar, Peter J. y Howard Colley. "Variations in F and Cl contents in apatites from magnetite—apatite ores in northern chile, and their ore-genetic implications". Mineralogical Magazine 60, n.º 399 (abril de 1996): 285–301. http://dx.doi.org/10.1180/minmag.1996.060.399.04.
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AbstractMagnetite—apatite deposits associated with the Atacama Fault Zone of northern Chile are interpreted here, on field criteria, as being the products either of hydrothermal fluids with a strong magmatic signature, or of late-stage Fe-rich magmas mixed with an aqueous fluid. Even in the Chilean iron belt, apatite-rich magnetite deposits are a rarity. Variations in F- and Cl- contents in apatites, strongly zoned with respect to halogens, are indicative of primary variations in fHF and fHCI in the hydrothermal fluids. Small variations in halogen fugacities in the aqueous fluid are capable of buffering large variations in halogen content within apatite crystals in equilibrium with that fluid. The recorded halogen zonation profiles are inconsistent with crystallization of the apatites simply from a volatile-rich, late-stage fractionation Fe-rich magma, or its derived magmatic vapour. It is more likely that they are the result of mineral—fluid buffering with a fluid that represents the mixing of a magmatically-derived aqueous fluid with a meteoric fluid that has variably scavenged Ca and Cl from within the country rocks. The source magma of the former is probably an Fe-P enriched acidic magma, derived by fractionation of primary calc-alkaline basic magmas.
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Rohanizadeh, Ramin y Racquel Z. LeGeros. "Novel Method of Hydroxyapatite Coating on Titanium Using Chemical Deposition". Key Engineering Materials 361-363 (noviembre de 2007): 617–20. http://dx.doi.org/10.4028/www.scientific.net/kem.361-363.617.
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The aim of this study was to deposit an adherent apatite coating on titanium substrate using a two-step chemical deposition method. First, titanium substrates were immersed in an acidic solution containing calcium and phosphate ions, resulting in the deposition of a monetite (CaHPO4) coating. Second, the monetite crystals were converted to apatite by hydrolysis in NaOH solution. Composition and morphology of the initial and final coatings were identified using X-ray diffraction (XRD), Scanning Electron Microscopy, and Energy Dispersive Spectroscopy (EDS). The final coating was porous and the apatite crystals were agglomerated and followed the outline of the large monetite crystals. The average tensile bond of the coating was 5.2 MPa and cohesion failures were observed more frequently than adhesion failures. The coating adhesion measured using scratch test was 13.1N. In conclusion, this study showed the potential of a two-step chemical deposition method for depositing an adherent coating of apatite at low temperatures.
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Kogarko, Lia. "Chemical Composition and Petrogenetic Implications of Apatite in the Khibiny Apatite-Nepheline Deposits (Kola Peninsula)". Minerals 8, n.º 11 (16 de noviembre de 2018): 532. http://dx.doi.org/10.3390/min8110532.
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Khibiny, one of the largest of the world’s peralkaline intrusions, hosts gigantic apatite deposits. Apatite is represented by F-apatite and it contains exceptionally high concentration of SrO. (4.5 wt % on average) and increased amounts of rare earth elements (REEs; up to 8891 ppm). Such enrichment of apatite ores in REEs defined Khibiny deposit as world-class deposit with resources reaching several millions tons REE2O3. Apatite from the Khibina alkaline complex is characterized by the significant enrichment in light REEs relative to the heavy REEs (with average Ce/Yb ratio of 682) and the absence of a negative Eu anomaly. The obtained geochemical signature of apatite suggests a residual character of the Khibiny alkaline magma and it indicates that the differentiation of the primary olivine-melanephelinitic magma developed without fractionation of plagioclase which is the main mineral-concentrator of Sr and Eu in basaltic magmatic systems. The compositional evolution of the Khibiny apatite in the vertical section of the intrusion reflects primary fractionation processes in the alkaline magma that differentiated in situ. The main mechanism for the formation of the apatite-nepheline deposits was the gravitational settling of large nepheline crystals in the lower part of the magma chamber, while very small apatite crystals were suspended in a convective magma, and, together with the melt, were concentrated in its upper part of the magmatic chamber.
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Müller, Frank A., Lenka Müller, Daniel Caillard y Egle Conforto. "Preferred growth orientation of biomimetic apatite crystals". Journal of Crystal Growth 304, n.º 2 (junio de 2007): 464–71. http://dx.doi.org/10.1016/j.jcrysgro.2007.03.014.
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Su, X. W. y F. Z. Cui. "Direct observations on apatite crystals in ivory". Journal of Materials Science Letters 16, n.º 14 (julio de 1997): 1198–200. http://dx.doi.org/10.1007/bf02765409.
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Tanimoto, K., T. Le, L. Zhu, J. Chen, J. D. B. Featherstone, W. Li y P. DenBesten. "Effects of Fluoride on the Interactions between Amelogenin and Apatite Crystals". Journal of Dental Research 87, n.º 1 (enero de 2008): 39–44. http://dx.doi.org/10.1177/154405910808700106.
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Fluorosed enamel is more porous and less mineralized, possibly related to altered amelogenin-modulated crystal growth. The purpose of this study was to examine the role of fluoride in interactions between amelogenin and apatite crystals. Recombinant human amelogenin (rh174) was bound to carbonated hydroxyapatite containing various amounts of fluoride, and analyzed by protein assay, SDS PAGE, and AFM. Interactions between rh174 and fluoride were assayed by isothermal titration calorimetry (ITC). The initial binding rate of rh174, as well as total amount of rh174 bound to fluoride-containing carbonated hydroxyapatite, was greater than that in the control carbonated hydroxyapatite. Fluoride in solution at physiologic (5.3 micromolar, or 0.1 ppm) concentrations showed no significant effect on binding, but higher fluoride levels significantly decreased protein binding. ITC showed no interactions between fluoride and rh174. These results suggest that fluoride incorporation into the crystal lattice alters the crystal surface to enhance amelogenin binding, with no direct interactions between fluoride and amelogenin.
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Daneshvar, Narges, Hossein Azizi, Yoshihiro Asahara, Motohiro Tsuboi y Mahdi Hosseini. "Rare Earth Elements and Sr Isotope Ratios of Large Apatite Crystals in Ghareh Bagh Mica Mine, NW Iran: Tracing for Petrogenesis and Mineralization". Minerals 10, n.º 9 (22 de septiembre de 2020): 833. http://dx.doi.org/10.3390/min10090833.
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The 320 Ma Ghareh Bagh mica mine is the only active mica mine in northwest Iran, and hosts Mg-bearing biotite (phlogopite) with apatite, epidote, and calcite. Chemical investigation of apatite infers the high abundances of the rare earth elements (REEs up to 5619 ppm), higher ratios of the LREE/HREE ((La/Yb)N = 28.5–36.7)) and high content of Y (236–497 ppm). REE pattern in the apatite and host A-type granite is almost the same. Ghareh Bagh apatite formed from the early magmatic-hydrothermal exsolved fluids at the high temperature from the Ghushchi alkali feldspar granite. The apatite crystals came up as suspension grains and precipitated in the brecciated zone. The early magmatic-hydrothermal fluids settle phlogopite, epidote, chlorite, K-feldspar and albite down in the brecciation zone. Due to the precipitation of these minerals, the late-stage fluids with low contents of Na+, Ca2+ and REE affected the early stage of alteration minerals. The high ratios of 87Sr/86Sr (0.70917 to 0.70950) are more consistent with crustal sources for the apatite large crystals. The same ages (320 Ma) for both brecciated mica veins and host alkali feldspar granites infer the apatite and paragenesis minerals were related to host granite A-type granite in the Ghareh Bagh area.
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Azadbakht, Zeinab, David Lentz y Christopher McFarlane. "Apatite Chemical Compositions from Acadian-Related Granitoids of New Brunswick, Canada: Implications for Petrogenesis and Metallogenesis". Minerals 8, n.º 12 (17 de diciembre de 2018): 598. http://dx.doi.org/10.3390/min8120598.
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The geochemistry of apatite crystals from fifteen fertile and infertile Acadian-related granitoids of New Brunswick (Canada) was studied in situ, using electron microprobe and laser ablation-inductively coupled plasma-mass spectrometry to further investigate petrogenesis and fertility index among these intrusions. The results indicate a clear geochemical contrast between barren and mineralized samples where apatite grains from barren intrusions are the most hydrous (OH > 0.3 wt. %), with lowest Mn (<1700 ppm), Fe (<800 ppm), and Sn (<0.01 ppm). In contrast, apatite grains from Cu-Mo related intrusions are distinguished by higher Cl (>0.1 wt. %), (La/Yb)N ratios of 21.17, (Eu/Eu*)N ratios of 0.30, and LREE/HREE ratios of 6.03. Apatites from Sn-W related magmatic suites have the highest F (>3 wt. %), Mn (>5350 ppm), Fe (>2200 ppm), Y (>4900 ppm), Sn (>2 ppm), and the lowest Cl (<0.01 wt. %), Sr (<60 ppm), U (<18 ppm), Th (<29 ppm), (Eu/Eu*)N ratios (<0.01), and (La/Yb)N ratios (<0.88). Lastly, apatite grains from Mo-bearing systems have the lowest SiO2 (<0.4 wt. %), Sr (<33 ppm), Th (<28 ppm), a moderate Mn (~3800 ppm), Y (~3500 ppm), and highest FeOt (<0.9 wt. %). However, the results indicated apatite Mn, Sr, LREE/HREE, and (Eu/Eu*)N ratios as the best fertility indices used for discriminating barren from fertile granite intrusions.
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Popov, Daniil V. y Richard A. Spikings. "Numerical Modelling of Radiogenic Ingrowth and Diffusion of Pb in Apatite Inclusions with Variable Shape and U-Th Zonation". Minerals 11, n.º 4 (31 de marzo de 2021): 364. http://dx.doi.org/10.3390/min11040364.
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The fundamental premise of apatite U-Th-Pb thermochronology is that radiogenic Pb is redistributed by volume diffusion. In practice, it is often additionally assumed that crystals (1) lose radiogenic Pb to an infinite reservoir, (2) have a simple geometry and (3) are chemically homogeneous. Here we explore the significance of the latter three assumptions by numerical modelling of Pb radiogenic ingrowth and diffusion in apatite inclusions within other minerals. Our results indicate that the host minerals are likely to hamper diffusive Pb loss from the apatite inclusions by limiting the Pb flux across their boundaries, and thus the thermal histories that are reconstructed assuming a fully open boundary may be significantly inaccurate, precluding a meaningful interpretation. We also find that when apatite boundaries are flux-limited, heterogeneities in U and Th concertation within apatite have subordinate effect on bulk-grain U-Th-Pb dates and can cause intra-grain U-Th-Pb dates to increase towards the boundaries. Finally, we show that it is important to correctly account for crystal geometry when modelling intra-grain U-Th-Pb dates. We suggest that the effect of surrounding minerals on diffusive Pb loss from apatite (and loss of other radiogenic isotopes from other minerals) should be examined more closely in future research.
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Abdullin, Fanis, Luigi A. Solari, Jesús Solé y Carlos Ortega-Obregón. "Technical note: LA–ICP-MS U–Pb dating of unetched and etched apatites". Geochronology 3, n.º 1 (20 de enero de 2021): 59–65. http://dx.doi.org/10.5194/gchron-3-59-2021.
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Abstract. The same unetched and chemically etched apatite crystals from five rock samples were dated by the U–Pb method via laser ablation inductively coupled plasma mass spectrometry (LA–ICP-MS). The objective of this study is to test whether chemical etching required for apatite fission track analysis impacts the precision and accuracy of apatite U–Pb geochronology. The results of this experiment suggest that etching has insignificant effects on the accuracy of apatite U–Pb ages obtained by LA–ICP-MS. Therefore, LA–ICP-MS is reliable for U–Pb analysis as part of apatite fission track and U–Pb double dating.
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Gawęda, Aleksandra, Krzysztof Szopa y David Chew. "LA-ICP-MS U-Pb dating and REE patterns of apatite from the Tatra Mountains, Poland as a monitor of the regional tectonomagmatic activity". Geochronometria 41, n.º 4 (1 de diciembre de 2014): 306–14. http://dx.doi.org/10.2478/s13386-013-0171-0.
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Abstract This study presents apatite LA-ICP-MS U-Pb age and trace elements concentrations data from different granite types from the Tatra Mountains, Poland. Apatite from monazite and xenotime-bearing High Tatra granite was dated at 339 ± 5 Ma. The apatite LREE patterns reflect two types of magmas that contributed to this layered magma series. Apatite from a hybrid allanite-bearing diorite from the Goryczkowa Unit was dated at 340 ± 4 Ma with apatite LREE depletion reflecting the role of allanite and titanite during apatite crystallization. Apatite crystals from a hybrid cumulative rock from the Western Tatra Mountains were dated at 344 ± 3 Ma. Apatite is one of the main REE carriers in this sample and exhibit flat REE patterns. Taking into account the relatively low closure temperature of the U-Pb system in apatite (350–550°C), the c. 340 Ma apatite ages mark the end of high temperature tectonometamorphic activity in the Tatra Mountains.
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Deng, Chun Lin, Ying Jun Wang, Ji Yong Chen, Hua De Zheng, Hu Chen, De Gui Zhang y Xing Dong Zhang. "Growth of Apatite in Bovine Serums on Porous HA/TCP Ceramics". Key Engineering Materials 368-372 (febrero de 2008): 1184–86. http://dx.doi.org/10.4028/www.scientific.net/kem.368-372.1184.
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Porous HA/TCP bioceramics were immersed in pure bovine serum to observe the growth and formation of apatite. HRTEM, FTIR, and SEM coupled with EDS were used for the characterization of immersed samples. SEM results showed that some beamed crystals formed on the surface of ceramics granules, and with postponement of immersion time, crystals extended and became bigger, strap-like crystals became sheet-like crystals. HRTEM observations indicated that new-formed crystals developed along axes direction according to parallel layers. IR spectrum showed CO3 2- characteristic peaks existed besides O-P-O and OH- characteristic peaks. EDS results showed that calcium and phosphor ratio was 1.95 (mol ratio). The results indicated that bovine serums were advantaged to bone-like apatite formation.
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Hopwood, Jeremy D., Glyn R. Derrick, David R. Brown, Christopher D. Newman, John Haley, Richard Kershaw y Mike Collinge. "The Identification and Synthesis of Lead Apatite Minerals Formed in Lead Water Pipes". Journal of Chemistry 2016 (2016): 1–11. http://dx.doi.org/10.1155/2016/9074062.
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Phosphate is added to drinking water in the UK to minimise the release of lead from lead water pipes. The phosphate encourages the formation of insoluble lead apatites on the walls of the pipe. Hydroxylpyromorphite Pb5(PO4)3OH is the lead apatite that is most often used to model lead levels in tap water; however, its presence has not been confirmed. Our aims were to identify the lead pipe apatite and synthesise it. The synthetic mineral would then be used in future solubility studies to produce better predictions of lead levels in tap water. XRD and FTIR were used to characterise the minerals on a range of lead pipes. Pyromorphite and hydroxylpyromorphite were absent and instead a range of mixed calcium lead apatites were present. For every five lead ions in the general formula Pb5(PO4)3X between one and two ions were replaced with calcium and there was evidence of substitution ofPO43-by eitherCO32-orHPO42-. Calcium lead apatites with similar unit cell dimensions to those found on lead water pipes were then synthesised. The calcium : lead ratio in these reaction mixtures was in excess of 500 : 1 and the resulting crystals were shown by TEM to be nanosized rods and flakes. The synthetic apatites that most closely resembled the unit cell dimensions of the apatites on lead water pipes were shown to be Pb3.4Ca1.3(PO4)3Cl0.03OH0.97, Pb3.6Ca1.2(PO4)3Cl0.07OH0.93, and Pb3.6Ca1.2(PO4)3Cl0.27OH0.73.
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Okazaki, M. y R. Z. Legeros. "Properties of Heterogeneous Apatites Containing Magnesium, Fluoride, and Carbonate". Advances in Dental Research 10, n.º 2 (noviembre de 1996): 252–59. http://dx.doi.org/10.1177/08959374960100022201.
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Biological apatites present in the mineral phases of normal and pathological calcifications contain magnesium, Mg, and carbonate, CO3. As a consequence of fluctuations in the composition of the micro-environment, these apatites may sometimes form by heterogeneous precipitation. The purpose of this study was to investigate the properties of (Mg, CO3)-apatites formed heterogeneously in the presence of fluoride, F. Two types of fluoridated (Mg, CO3)-apatites formed from solutions with low and high levels of Mg were prepared at 80°C, pH 7.4. We prepared FMgCO3-MgCO 3AP (Type 1) by adding the F-containing solution to those containing calcium, Mg, and phosphate ions during the first half of the precipitation period. We prepared MgCO3-FMgCO3Ap (Type 2) by adding the F-containing solution during the final half of the period. The apatites were analyzed by x-ray diffraction (XRD), infrared absorption spectroscopy, and scanning electron microscopy (SEM). SEM and XRD analyses showed evidence of mixed crystals in the heterogeneous apatites. The presence of Mg inhibits, while F promotes, apatite crystal growth. In addition, Mg incorporation increased with increasing fluoride concentration. The extent of dissolution in acid buffer of both types of heterogeneous apatites increased with Mg: Type 1 > Type 2. These results suggest that the crystal and dissolution properties of heterogeneous fluoridated (Mg, C03)-apatites are greatly affected by the mode of F incorporation and Mg concentrations in the environment.
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Driessens, F. C. M., R. A. Terpstra, P. Bennema, J. H. M. Wöltgens y R. M. H. Verbeeck. "On the Possible Relation between Morphology and Precursors of the Crystallities in Calcified Tissues". Zeitschrift für Naturforschung C 42, n.º 7-8 (1 de agosto de 1987): 916–20. http://dx.doi.org/10.1515/znc-1987-7-831.
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Crystal structure data on hydroxyapatite, octocalcium phosphate and brushite have been used in order to predict their crystal morphology on the basis of the Hartman-Perdok theory. The predicted forms are pencil-like for hydroxyapatite, board-like for octocalcium phosphate and flattened needle-like for brushite. Although the biominerals in bone, dentine and tooth enamel have an apatite structure, their form is nbt pencil-like. This may partially be due to the fact that precursor phases are nucleated first in these tissues during mineralization and that these precursor phases are transformed later by topotactical reactions into compounds with apatite structure or that they serve as nuclei for ongrowth of apatite. The form of the mineral particles in mature bone and dentin is board-like which indicates that octocalcium phosphate might be their precursor phase. However, the form of the crystals in mature enamel is flattened needle-like which indicates that brushite is their precursor phase. It is argued that a possible difference in the nature of the precursor phase may be due primarily to differences in the cellular activities of the odontoblasts and osteoblasts as compared to those of the ameloblasts, and secondarily to matrix effects. In both cases, however, the main effect of the matrix seems to be that it acts as a mechanical barrier leading to a limited form and size and, of course, a certain orientation of the crystals, rather than as an agent for heterogeneous nucleation. The validity of the present considerations depends as yet on the assumption that the ions and molecules occurring in body fluids do not dominate the habit of calcium phosphate crystals.
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Xu, Bo, Guanyu Kou, Barbara Etschmann, Daiyue Liu y Joël Brugger. "Spectroscopic, Raman, EMPA, Micro-XRF and Micro-XANES Analyses of Sulphur Concentration and Oxidation State of Natural Apatite Crystals". Crystals 10, n.º 11 (12 de noviembre de 2020): 1032. http://dx.doi.org/10.3390/cryst10111032.
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Sulphur is the third most abundant volatile element in deep Earth systems. Analytical methods for accurately and efficiently determining the sulphur content and oxidation state in natural minerals are still lacking. Natural apatite is widely distributed in the Earth and incorporates a large amount of sulphur. Therefore, apatite is an ideal mineral for performing sulphur measurements. Here, we used spectroscopic, Raman, X-ray diffraction, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), electron microprobe (EMPA) and micro-X-ray fluorescence spectrometry (micro-XRF) analysis techniques and developed a new analytical approach (i.e., micro-X-ray absorption near-edge structure (micro-XANES) analysis of the sulphur K-edge) to investigate the chemical characteristics of natural apatite. These multiple methods were developed to measure in situ sulphur concentration and S oxidation states and to assess a potential natural apatite reference material. Apatite contains chemically homogeneous sulphur, with micro-XANES located at the peak energies corresponding to S6+ (sulphate; ~2482 eV), S4+ (sulfite; ~2478 eV), and S2− (sulphide; ~2467, 2470 and 2474 eV). The Durango apatite contains total S presented as SO3 at amount of 0.332 ± 0.012 wt.% (1σ), with a large amount of S6+ and a small contribution of S4+. The Kovdor apatite contains 44–100 ppm of S and is dominated by S6+. These results indicate that the Durango apatite crystallised under relative oxidising conditions, and the Kovdor apatite has a higher oxygen fugacity than Durango. In addition, this study indicates the potential use of the natural apatite reference material with its S composition and S oxidation state.
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Li, Chunmei, Hyoung-Joon Jin, Gregory D. Botsaris y David L. Kaplan. "Silk apatite composites from electrospun fibers". Journal of Materials Research 20, n.º 12 (1 de diciembre de 2005): 3374–84. http://dx.doi.org/10.1557/jmr.2005.0425.
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Human bone is a three-dimensional composite structure consisting of inorganic apatite crystals and organic collagen fibers. An attractive strategy for fabricating mimics of these types of composite biomaterials is to selectively grow apatite on polymers with control of structure, mechanical properties, and function. In the present study, silk/apatite composites were prepared by growing apatite on functionalized nanodiameter silk fibroin fibers prepared by electrospinning. The functionalized fibers were spun from an aqueous solution of silk/polyethylene oxide (PEO) (78/22 wt/wt) containing poly(L-aspartate) (poly-Asp), which was introduced as an analogue of noncollageous proteins normally found in bone. Silk fibroin associated with the acidic poly-Asp and acted as template for mineralization. Apatite mineral growth occurred preferentially along the longitudinal direction of the fibers, a feature that was not present in the absence of the combination of components at appropriate concentrations. Energy dispersive spectroscopy and x-ray diffraction confirmed that the mineral deposits were apatite. The results suggest that this approach can be used to form structures with potential utility for bone-related biomaterials based on the ability to control the interface wherein nucleation and crystal growth occur on the silk fibroin. With this level of inorganic–organic control, coupled with the unique mechanical properties, slow rates of biodegradation, and polymorphic features of this type of proteins, new opportunities emerge for utility of biomaterials.
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Yang, Xiu Dong, Li Zhao Teng, Jian Lu, Qing Rong Wei, Hui Wang, Ji Yong Chen y Bang Cheng Yang. "Biomimetic Coating on Titanium Metal and Its Excellent Cell Proliferation". Key Engineering Materials 330-332 (febrero de 2007): 613–16. http://dx.doi.org/10.4028/www.scientific.net/kem.330-332.613.
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Biomimetic coating on roughed titanium plates were prepared in this work by a cathode deposition method in calcium phosphate solution electrolyte. The coatings of plate-like apatite crystals were deposited on the titanium plates under a constant potential of 2.0V for 60 min at 37. The coating crystals were identified to be carbonate-containing apatite (bone-like apatite) by X-ray diffraction and scanning electronic microscopy. The cell proliferation and adhesion of L929 cells on the titanium metal plates with biomimetic coating and the titanium plates with roughed-only were tested. The results showed that biomimetic coating on titanium surface can enhance the materials bioactivity. The study indicated that cathode method is potential to prepare biomimetic coating on titanium implants with excellent bioactivity.
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Suetsugu, Yasushi, Toshiyuki Ikoma, Masanori Kikuchi y M. Tanaka. "Single Crystal Growth and Structure Analysis of AB-Type Carbonate Apatite". Key Engineering Materials 288-289 (junio de 2005): 525–28. http://dx.doi.org/10.4028/www.scientific.net/kem.288-289.525.
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Single crystals of AB-type carbonate apatite were grown by a CaCO3-Na2CO3 flux method under high pressure of Ar gas. The crystals obtained were hexagonal prismatic elongated along the c-axis with the length of 2mm and the diameter of 0.3mm at a maximum. Chemical formula was Ca8.8Na1.2[(PO4)4.8(CO3)1.2]CO3 and the space group was hexagonal P6 with cell parameters a = 0.9379(2)nm, c = 0.6935(1)nm. The detailed crystal structure determined with a reliability factor Rw = 0.047 indicated that the triangular plane of carbonate ion occupying B-site was slanted off the crystallographic mirror plane and the angle of the carbonate triangle with the mirror plane varied depending on Na-substitution of adjacent Ca sites whilst the A-site carbonate ion was parallel to the c-axis.
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Hayakawa, Tomoyasu, Masakazu Kawashita, Gikan H. Takaoka y Toshiki Miyazaki. "Effect of pulse current on structure and adhesion of apatite electrochemically deposited onto titanium substrates". Journal of Materials Research 23, n.º 12 (diciembre de 2008): 3176–83. http://dx.doi.org/10.1557/jmr.2008.0386.
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Apatite films were deposited onto titanium (Ti) metal substrates by an electrodeposition method under a pulse current. Metastable calcium phosphate solution was used as the electrolyte. The ion concentration of the solution was 1.5 times that of human body fluid, but the solution did not contain magnesium ions at 36.5 °C. We used an average current density of 0.01 A/cm2 and current-on time (TON) equal to current-off time (TOFF) of 10 ms, 100 ms, 1 s, and 15 s. The adhesive strength between apatite and Ti substrates were relatively high at TON = TOFF = 10 ms. It is considered that small calcium phosphate (C–P) crystals with low crystallinity were deposited on the Ti surface without reacting with other C–P crystals, H2O, and HCO3− in the surrounding environment. This resulted in relaxation of the lattice mismatch and enhancement of the adhesive strength between the apatite crystals and Ti substrates.
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Zhao, Ying, Tian Ying Xiong, Tie Fan Li, J. Wu, Hua-Zi Jin y Li Bin Wang. "Study on the Bioactivity of Anodic Oxidized Titanium Alloy Induced by Alkali Treatment". Key Engineering Materials 309-311 (mayo de 2006): 383–86. http://dx.doi.org/10.4028/www.scientific.net/kem.309-311.383.
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Alkali treatment induced to form bonelike apatite layer on the surface of the anodic oxidized Ti6Al4V in 1.5 SBF. It was observed that some spherical apatite crystals were deposited on the surface of the sample for only 1 d. They gradually grew to cover the whole surface of the sample with further increasing soaking time. After 7 days of soaking in 1.5 SBF, apatite covered all the surfaces of the titanium alloys, and they packed very densely and uniformly. At the same time, large amount of new-formed apatite nuclei occurred on the first layer of apatite. The EDS and XRD results proved that all the new-formed phases were composed of apatite. Mechanism of the bioactivity of the anodic oxidized titanium alloys was related to the Ti-OH group formation, and the Ti-OH group would induce apatite formation in SBF.
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Yokogawa, Yoshiyuki, M. Tagaki, Y. Siotsu y Makoto Watanabe. "Protein Loaded Apatite Hydrogel and Protein Release from Its Cake". Key Engineering Materials 330-332 (febrero de 2007): 1037–40. http://dx.doi.org/10.4028/www.scientific.net/kem.330-332.1037.
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The time-dependent variation of the protein release from protein incorporated apatite cake in PBS solution was studied. When protein incorporated apatite cakes were immersed in PBS, the volume of cakes dropped for 1 day of soaking period and the shrinkage of specimen seems to be stabilized after 2 or 3 days soaking in PBS. The quantity of released protein from protein incorporated apatite cake was increased with an increase of soaking period. Around several % of protein came from the protein incorporated apatite cake in PBS for 2 weeks. The time-dependent protein release was relatively high for 1 day of soaking period, after that it slowly decreased. Compared to the decrease in volume of cake, the quantity ratio of released protein and total incorporated protein was less, which may be associated with recrystallization of the apatite hydrogel. FE-SEM observation revealed both crystals formed in air or under N2 atmosphere had similar rod like shape, and seems to be almost same in size. The change of surface appearance between 1 day and 4 days or longer soaking may be due to the dissolution of the surface layer and its recrystallization. The aggregate of apatite crystals formed in air is found to be compact, but some small cavities are observed in the specimens soaked in PBS for 4 – 11 days. The particle size of protein incorporated apatite were almost similar, independent on the soaking period. But the shape of apatite in aqueous solution is changing from square and angular shape to round shape.
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Kim, Hyun-Man, Young-Seol Kim, Kyung-Mi Woo, Su-Jin Park, Christian Rey, Yoonji Kim, Jung-Keun Kim y Jea Seung Ko. "Dissolution of poorly crystalline apatite crystals by osteoclasts determined on artificial thin-film apatite". Journal of Biomedical Materials Research 56, n.º 2 (2001): 250–56. http://dx.doi.org/10.1002/1097-4636(200108)56:2<250::aid-jbm1092>3.0.co;2-s.
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