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Artículos de revistas sobre el tema "Crystals Apatite. Silicon crystals"

Autor: Grafiati

Publicado: 4 de junio de 2021

Última modificación: 9 de febrero de 2022

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1

Ma, Hai Zhu, Fang Huang, Shi Rong Liu, Bo Xu y Hua Long Liu. "Classification and Morphological Structure of Scale in the Process of Alumina Production High Pressure Digestion". Advanced Materials Research 960-961 (junio de 2014): 274–80. http://dx.doi.org/10.4028/www.scientific.net/amr.960-961.274.

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The chemical composition, phase component and morphology characteristics of scale were researched by chemical analysis, XRD, SEM and TEM. The results show that the scale can be divided into iron minerals, silicon minerals, Ca-Ti-Mg minerals and aluminum hydroxide. Alumogoethite and micro-fine sodium-silicon slag fill in the gaps between the neat and bulky hematite crystals. Microgranular hydrated garnet and olivine fill in the gaps between the goethite crystals with a dense layered structure, accompanied by a small amount of galena and apatite precipitation particles. Perovskite and magnesium hydroxide have five periodic sedimentary cycles, forming an alternating sedimentary layer structure. Aluminum hydroxide forms thick scale and presents two kinds of typical structures, spherulitic and laminated. The research provides the theoretical basis for preventing and controlling scale in high-pressure digester group.

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2

Barbee, Olivia, Craig Chesner y Chad Deering. "Quartz crystals in Toba rhyolites show textures symptomatic of rapid crystallization". American Mineralogist 105, n.º 2 (1 de febrero de 2020): 194–226. http://dx.doi.org/10.2138/am-2020-6947.

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Abstract Textural and chemical heterogeneities in igneous quartz crystals preserve unique records of silicic magma evolution, yet their origins and applications are controversial. To improve our understanding of quartz textures and their formation, we examine those in crystal-laden rhyolites produced by the 74 ka Toba supereruption (>2800 km3) and its post-caldera extrusions. Quartz crystals in these deposits can reach unusually large sizes (10–20 mm) and are rife with imperfections and disequilibrium features, including embayments, melt inclusions, titanomagnetite and apatite inclusions, spongy morphologies, hollow faces, subgrain boundaries, multiple growth centers, and Ti-enriched arborescent zoning. Using a combination of qualitative and quantitative analyses (petrography, CL, EBSD, X-ray CT, LA-ICPMS), we determine that those textures commonly thought to signify crystal resorption, crystal deformation, synneusis, or fluctuating P–T conditions are here a consequence of rapid disequilibrium crystal growth. Most importantly, we discover that an overarching process of disequilibrium crystallization is manifested among these crystal features. We propose a model whereby early skeletal to dendritic quartz growth creates a causal sequence of textures derived from lattice mistakes that then proliferate during subsequent stages of slower polyhedral growth. In a reversed sequence, the same structural instabilities and defects form when slow polyhedral growth transitions late to fast skeletal-dendritic growth. Such morphological transitions result in texture interdependencies that become recorded in the textural-chemical stratigraphy of quartz, which may be unique to each crystal. Similar findings in petrologic experimental studies allow us to trace the textural network back to strong degrees of undercooling and supersaturation in the host melt, conditions likely introduced by dynamic magmatic processes acting on short geologic timescales. Because the textural network can manifest in single crystals, the overall morphology and chemistry of erupted quartz can reflect not only its last but its earliest growth behavior in the melt. Thus, our findings imply that thermodynamic disequilibrium crystallization can account for primary textural and chemical heterogeneities preserved in igneous quartz and may impact the application of quartz as a petrologic tool.

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3

Szopa, Krzysztof, Roman Włodyka y David Chew. "LA-ICP-MS U-Pb apatite dating of Lower Cretaceous rocks from teschenite-picrite association in the Silesian Unit (southern Poland)". Geologica Carpathica 65, n.º 4 (1 de agosto de 2014): 273–84. http://dx.doi.org/10.2478/geoca-2014-0018.

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Abstract The main products of volcanic activity in the teschenite-picrite association (TPA) are shallow, sub-volcanic intrusions, which predominate over extrusive volcanic rocks. They comprise a wide range of intrusive rocks which fall into two main groups: alkaline (teschenite, picrite, syenite, lamprophyre) and subalkaline (dolerite). Previous 40Ar/39Ar and 40K/40Ar dating of these rocks in the Polish Outer Western Carpathians, performed on kaersutite, sub-silicic diopside, phlogopite/biotite as well as on whole rock samples has yielded Early Cretaceous ages. Fluorapatite crystals were dated by the U-Pb LA-ICP-MS method to obtain the age of selected magmatic rocks (teschenite, lamprophyre) from the Cieszyn igneous province. Apatite-bearing samples from Boguszowice, Puńców and Lipowa yield U-Pb ages of 103± 20 Ma, 119.6 ± 3.2 Ma and 126.5 ± 8.8 Ma, respectively. The weighted average age for all three samples is 117.8 ± 7.3 Ma (MSWD = 2.7). The considerably smaller dispersion in the apatite ages compared to the published amphibole and biotite ages is probably caused by the U-Pb system in apatite being less susceptible to the effects of hydrothermal alternation than the 40Ar/39Ar or 40K/40Ar system in amphibole and/or biotite. Available data suggest that volcanic activity in the Silesian Basin took place from 128 to 103 Ma with the the main magmatic phase constrained to 128-120 Ma.

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4

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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5

Aizawa, Mamoru, Nelesh Patel, Alexandra E. Porter, Serena Best y William Bonfield. "Syntheses of Silicon-Containing Apatite Fibres by a Homogeneous Precipitation Method and Their Characterization". Key Engineering Materials 309-311 (mayo de 2006): 1129–32. http://dx.doi.org/10.4028/www.scientific.net/kem.309-311.1129.

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Silicon-containing apatite (Si-HAp) fibres were successfully synthesized by a homogeneous precipitation method. The resulting Si-HAp fibres were composed of carbonate-containing apatite fibres with preferred orientation in the c-axis. The Si contents in the Si-HAp fibres could be controlled by the Si concentration of the starting solutions. TEM observation indicated that the Si-HAp fibres were of single crystal. The Si-HAp fibres have potential as novel materials for high-performance biomedical devices.

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6

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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7

López, Cefe. "Silicon Photonic Crystals". Optics and Photonics News 20, n.º 1 (1 de enero de 2009): 28. http://dx.doi.org/10.1364/opn.20.1.000028.

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8

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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9

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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10

Rusiecka, Monika K. y Don R. Baker. "Monazite and xenotime solubility in hydrous, boron-bearing rhyolitic melt". American Mineralogist 104, n.º 8 (1 de agosto de 2019): 1117–30. http://dx.doi.org/10.2138/am-2019-6931.

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Abstract We conducted a series of monazite and xenotime dissolution experiments in a boron-bearing silicic melt at 1000–1400 °C and 800 MPa in a piston-cylinder apparatus. We present new measurements of monazite and xenotime solubility in hydrous (~3 wt% water), boron-bearing rhyolitic melts, as well as the diffusivities of the essential structural constituents of those minerals (LREE, P, and Y). We compare our results to the previous studies and discuss the implications of this study on the understanding of natural, silicic (granitic/rhyolitic) systems. We propose one equation describing the relationship between the solubility of xenotime and temperature in hydrous rhyolitic melts: ln ⁡ Y = 18.3 ± 0.3 − 125499 ± 3356 R T and another for monazite: ln ⁡ Σ LREE = 18.6 ± 1.5 − 129307 ± 18163 R T . In the presence of sufficient phosphorous, the concentration of LREE needed for monazite saturation is within the uncertainty of the Y concentration needed from xenotime saturation and indicates that in the case of equilibrium crystallization the mineral that forms will only depend on the availability of LREE and Y and HREE. Given the similarity of the solubility of xenotime to that of monazite, we propose that previously published models of monazite solubility in silicic melts can potentially be applied to xenotime, and could, like monazite, serve as a geothermometer. In the case of disequilibrium crystallization in front of rapidly growing crystals, Y will diffuse faster than LREE and xenotime will only crystallize when LREE are depleted. We also found that the diffusion of Y is greater than the diffusion of P from dissolving xenotime, unlike the similar diffusivities of LREE and P during monazite dissolution. The significant difference between Y and P diffusivities suggests that the components forming xenotime diffuse as separate entities rather than molecular complexes. The dissolution of phosphates (monazite, xenotime, apatite) in hydrous, silicic melts with the addition of boron leads to liquid-liquid immiscibility at high temperatures where the saturation values of P and either light rare earth elements or Y are in the weight percent range. Immiscibility is not observable at low, magmatic temperatures, most probably due to the lower concentrations of P2O5 necessary for phosphate saturation at these conditions; however addition of other components, notably F, may result in liquid-liquid immiscibility at magmatic temperatures.

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11

Birner, A., R. B. Wehrspohn, U. M. Gösele y K. Busch. "Silicon-Based Photonic Crystals". Advanced Materials 13, n.º 6 (marzo de 2001): 377–88. http://dx.doi.org/10.1002/1521-4095(200103)13:6<377::aid-adma377>3.0.co;2-x.

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12

Tanaka, M. y A. Peuto. "Density of Silicon Crystals". Metrologia 31, n.º 3 (1 de enero de 1994): 219–30. http://dx.doi.org/10.1088/0026-1394/31/3/008.

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13

Möller, H. J. "Wafering of silicon crystals". physica status solidi (a) 203, n.º 4 (marzo de 2006): 659–69. http://dx.doi.org/10.1002/pssa.200564508.

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14

Liu, Xuanyong, Ricky K. Y. Fu, Paul K. Chu y Chuanxian Ding. "Mechanism of apatite formation on hydrogen plasma-implanted single-crystal silicon". Applied Physics Letters 85, n.º 16 (18 de octubre de 2004): 3623–25. http://dx.doi.org/10.1063/1.1807009.

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15

Higuchi, Mikio, Kohei Kodaira y Susumu Nakayama. "Nonstoichiometry in apatite-type neodymium silicate single crystals". Journal of Crystal Growth 216, n.º 1-4 (junio de 2000): 317–21. http://dx.doi.org/10.1016/s0022-0248(00)00421-8.

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16

Okazaki, M., Y. Yoshida, S. Yamaguchi, M. Kaneno y J. C. Elliott. "Affinity binding phenomena of DNA onto apatite crystals". Biomaterials 22, n.º 18 (septiembre de 2001): 2459–64. http://dx.doi.org/10.1016/s0142-9612(00)00433-6.

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17

Somiya, S., Koji IOKU y M. Yoshimura. "Hydrothermal Synthesis and Characterization of Fine Apatite Crystals". Materials Science Forum 34-36 (enero de 1991): 371–78. http://dx.doi.org/10.4028/www.scientific.net/msf.34-36.371.

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18

Li-Yu, J. "Calcium apatite crystals in synovial fluid rice bodies". Annals of the Rheumatic Diseases 61, n.º 5 (1 de mayo de 2002): 387–90. http://dx.doi.org/10.1136/ard.61.5.387.

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19

Su, X., K. Sun, F. Z. Cui y W. J. Landis. "Organization of apatite crystals in human woven bone". Bone 32, n.º 2 (febrero de 2003): 150–62. http://dx.doi.org/10.1016/s8756-3282(02)00945-6.

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20

Nelson, D. G. A. y J. C. Barry. "High resolution electron microscopy of nonstoichiometric apatite crystals". Anatomical Record 224, n.º 2 (junio de 1989): 265–76. http://dx.doi.org/10.1002/ar.1092240217.

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21

TORRALBA, Karina D., Dorothy JOHNSON y Francisco P. QUISMORIO. "Carbonate apatite crystals in primary normophosphatemic tumoral calcinosis". APLAR Journal of Rheumatology 9, n.º 3 (septiembre de 2006): 294–97. http://dx.doi.org/10.1111/j.1479-8077.2006.00180.x.

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22

DenBesten, Pamela K., Li Zhu, Wu Li, Kotaro Tanimoto, Haichuan Liu y Halina E. Witkowska. "Fluoride incorporation into apatite crystals delays amelogenin hydrolysis". European Journal of Oral Sciences 119 (diciembre de 2011): 3–7. http://dx.doi.org/10.1111/j.1600-0722.2011.00903.x.

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23

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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24

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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25

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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26

Nakamura, Minoru. "Copper Complexes in Silicon Crystals". Defect and Diffusion Forum 200-202 (noviembre de 2001): 135–44. http://dx.doi.org/10.4028/www.scientific.net/ddf.200-202.135.

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27

Kakimoto, Koichi, Bing Gao, Xin Liu y Satoshi Nakano. "Growth of semiconductor silicon crystals". Progress in Crystal Growth and Characterization of Materials 62, n.º 2 (junio de 2016): 273–85. http://dx.doi.org/10.1016/j.pcrysgrow.2016.04.014.

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28

Gutkin, Mikhail Yu, Alexander G. Sheinerman y Tatiana S. Argunova. "Micropipes in silicon carbide crystals". physica status solidi (c) 6, n.º 8 (agosto de 2009): 1942–47. http://dx.doi.org/10.1002/pssc.200881454.

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29

Mallick, Shrestha Basu, Il Woong Jung, Aaron M. Meisner, J. Provine, Roger T. Howe y Olav Solgaard. "Multilayered Monolithic Silicon Photonic Crystals". IEEE Photonics Technology Letters 23, n.º 11 (junio de 2011): 730–32. http://dx.doi.org/10.1109/lpt.2011.2132698.

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30

Karachinov, V. A. "Negative crystals of silicon carbide". Technical Physics 47, n.º 4 (abril de 2002): 432–37. http://dx.doi.org/10.1134/1.1470590.

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31

Temelkuran, B., Mehmet Bayindir, E. Ozbay, J. P. Kavanaugh, M. M. Sigalas y G. Tuttle. "Quasimetallic silicon micromachined photonic crystals". Applied Physics Letters 78, n.º 3 (15 de enero de 2001): 264–66. http://dx.doi.org/10.1063/1.1339256.

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32

Lan, C. W., C. F. Yang, A. Lan, M. Yang, A. Yu, H. P. Hsu, B. Hsu y C. Hsu. "Engineering silicon crystals for photovoltaics". CrystEngComm 18, n.º 9 (2016): 1474–85. http://dx.doi.org/10.1039/c5ce02343b.

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33

Raineri, V., V. Privitera, G. Galvagno, F. Priolo y E. Rimini. "Channeling implants in silicon crystals". Materials Chemistry and Physics 38, n.º 2 (julio de 1994): 105–30. http://dx.doi.org/10.1016/0254-0584(94)90001-9.

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34

Iijima, Mayumi, Yutaka Moriwaki, Yutaka Doi y Yoshinori Kuboki. "The orientation of apatite crystals in Lingula unguis shell." Japanese Journal of Oral Biology 30, n.º 1 (1988): 20–30. http://dx.doi.org/10.2330/joralbiosci1965.30.20.

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35

Suzuki, Takaomi, Go Hirose y Shuji Oishi. "Contact angle of water droplet on apatite single crystals". Materials Research Bulletin 39, n.º 1 (enero de 2004): 103–8. http://dx.doi.org/10.1016/j.materresbull.2003.09.013.

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36

Mohr, W. "On the origin of rice bodies with apatite crystals". Annals of the Rheumatic Diseases 62, n.º 9 (1 de septiembre de 2003): 910–11. http://dx.doi.org/10.1136/ard.62.9.910.

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37

Grynpas, Marc D. y Sidney Omelon. "Transient precursor strategy or very small biological apatite crystals?" Bone 41, n.º 2 (agosto de 2007): 162–64. http://dx.doi.org/10.1016/j.bone.2007.04.176.

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38

Kakei, M. M., T. Sakae, H. Mishima y M. Yoshikawa. "Effect of estrogen deficiency on formation of apatite crystals". Bone 48 (mayo de 2011): S117. http://dx.doi.org/10.1016/j.bone.2011.03.210.

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39

Perelygin, V. P., R. I. Petrova, S. G. Stetsenko, KH Murtazaev y N. T. Kashukeev. "On fission track dating of the terrestrial apatite crystals". International Journal of Radiation Applications and Instrumentation. Part D. Nuclear Tracks and Radiation Measurements 19, n.º 1-4 (enero de 1991): 725–28. http://dx.doi.org/10.1016/1359-0189(91)90300-7.

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40

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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41

Deng, Chun Lin, Ying Jun Wang, Yao Wu, Ying De Qin, Hong Song Fan, Ji Yong Chen y Xing Dong Zhang. "Apatite Formation on the Surface of Dense HA/TCP in Animals' Serums". Key Engineering Materials 336-338 (abril de 2007): 1542–44. http://dx.doi.org/10.4028/www.scientific.net/kem.336-338.1542.

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Dense HA/TCP bioceramics were immersed in pure bovine serum, rabbit serum and dog serum to observe apatite formation. Deposited crystals were examined using SEM. Results showed that some needle-like crystals formed on surface of sterilized HA/TCP, and needle crystals developed into sheet crystals and stick crystals after ceramics were immersed in bovine serum and rabbit serum respectively. The growth of crystals was maybe affected by the content of calcium, various kinds of albumen and alkaline phosphatase in different serums and the different pH of serum.

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42

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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43

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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44

Dang, Zhiya, Agnieszka Banas, Sara Azimi, Jiao Song, Mark Breese, Yong Yao, Shuvan Prashant Turaga, Gonzalo Recio-Sánchez, Andrew Bettiol y Jeroen Van Kan. "Silicon and porous silicon mid-infrared photonic crystals". Applied Physics A 112, n.º 3 (31 de mayo de 2013): 517–23. http://dx.doi.org/10.1007/s00339-013-7782-4.

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45

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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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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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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48

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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Kakei, Mitsuo, Toshiro Sakae, Hiroyuki Mishima y Masayoshi Yoshikawa. "Ultrastructure of Apatite Crystals Formed During Vascular Calcification in Humans". Journal of Hard Tissue Biology 18, n.º 3 (2009): 135–40. http://dx.doi.org/10.2485/jhtb.18.135.

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50

Sato, Kaori, Osamu Ikenoya, Yoshihito Shimazu y Takaaki Aoba. "Carbonation of Enamal Apatite Crystals: Lattice Substitutions and Surface Adsorption." Japanese Journal of Oral Biology 41, n.º 1 (1999): 61–68. http://dx.doi.org/10.2330/joralbiosci1965.41.61.

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