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  • 1
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 212 (1966), S. 498-499 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Two keratinized layers were mechanically separated from the outer scale surface of ventral and dorsal scales from a freshly shed skin of a boa constrictor (Constrictor constrictor). The fzeaog layer is very thin and fragile and pieces of it were present with both the outer and inner keratin ...
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0827
    Keywords: Bone ; Mineral ; Crystallinity ; Maturation ; Age
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The crystallinity of bone mineral at different stages of maturation has been measured by quantitative X-ray diffraction methods. Crystallinity measurements were made on tibial middiaphyses from 17-day embryonic chicks, newlyformed periosteal bone from embryonic chicks, and density-fractionated bone from post-hatch chickens from 5 weeks to 2 years of age. For a given animal age and degree of mineralization, crystallinity increases with animal age, indicating that changes in bone mineral occur even after mineralization is complete or nearly complete.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0827
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The properties of bone mineral change with age and maturation. Several investigators have suggested the presence of an initial or “precursor” calcium phosphate phase to help explain these differences. We have used solid state 31P magic angle sample spinning (MASS) nuclear magnetic resonance (NMR) and X-ray radial distribution function (RDF) analyses to characterize 11-and 17-day-old embryonic chick bone and fractions obtained from them by density fractionation. Density fractionation provides samples of bone containing Ca-P solid-phase deposits even younger and more homogeneous with respect to the age of mineral than the calcium phosphate (Ca-P) deposits in the whole bone samples. The analytical techniques yield no evidence for any distinct phase other than the poorly crystal-line hydroxyapatite phase characteristic of mature bone mineral. In particular, there is no detectable crystalline brushite [DCPD, CaHPO4 2H2O〈 1%] or amorphous calcium phosphate (〈 8–10%) in the most recently formed bone mineral. A sizeable portion of the phosphate groups exist as HPO4 2− in a brushite (DCPD)-like configuration. These acid phosphate moieties are apparently incorporated into the apatitic lattice. The most likely site for the brushite-like configuration is probably on the surface of the crystals.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 19 (1984), S. 723-736 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An investigation of the molecular structure of bone mineral and synthetic calcium phosphates was carried out using radial distribution function (RDF) techniques. The X-ray data were collected using CuKα and MoKα radiation to insure the validity of the RDFs. Synthetic preparations of hydroxyapatite (HA) varying in their crystal size and crystallinity, and amorphous calcium phosphate (ACP), were studied, as well as bone samples from a 1-year-old chicken and 16-day embryonic chicks. Mixtures of embryonic bone and synthetic ACP were also investigated. The RDFs of bone and crystalline HA samples are similar in peak position, and show evidence of an atomic order extending to 2.5 nm and beyond. The RDF of ACP differs from that of HA, showing only short range order up to 0.9 nm, as well as small differences in peak shape. The decrease in intensity of the RDF function with increasing distance (r), observed with both HA and bone samples can be related to a decrease in crystallinity and crystal size. The RDF data indicate there is no significant amount of ACP in either very young or mature bone. The RDFs of the embryonic bone + synthetic ACP mixtures showed that a small amount of ACP can be readily detected in a sample of bone with a poorly crystalline mineral phase; from this we estimate the threshold for detection of ACP in bone to be 12% or less.
    Type of Medium: Electronic Resource
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