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  • 1
    Electronic Resource
    Electronic Resource
    Three-Dimensional Crystalline Structure of Cellulose Triacetate II (1978)
    s.l. : American Chemical Society
    Macromolecules 11 (1978), S. 86-94 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma60061a016
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  • 2
    Electronic Resource
    Electronic Resource
    Disproportionation in mineral solid solutions: symmetry constraints on precipitate orientation and morphology. Implications for the study of oriented intergrowths (1994)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 27 (1994), S. 567-573 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Precipitation (exsolution) from mineral solid solutions is studied from the group-theoretical point of view. The symmetry of the oriented intergrowth (matrix and precipitates), including the precipitate morphology, is described by the intersection group, a subgroup of both the matrix and precipitate respective point groups. The index of the intersection group into the matrix group defines: (i) the number of orientation variants of the precipitate; (ii) the order of the subgroup of the matrix group, the symmetry elements of which generate the variants. Examples from the literature, in oxides and silicates, illustrate these principles and show how they can help to identify precipitation processes and derive genetic information from oriented intergrowths.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889894000750
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  • 3
    Electronic Resource
    Electronic Resource
    Structure, morphologie et macles des polymères (1979)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 35 (1979), S. 422-428 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Polymer crystal structures are tentatively grouped according to the relations between the symmetries of the macromolecular chain and the space group. Three possibilities occur: helical molecular symmetry (a) compatible with a crystalline lattice, or (b) incompatible, but with the chain axis parallel to the lattice principal axis; and low symmetry of the chain and lattice with random orientation of the chain. In the first two cases, the affinity between molecular and lattice symmetry allows us to describe the morphology and twinning of dilute-solution-grown crystals according to the classical laws. In the last case, these laws should be adjusted to the two-dimensional lattice which characterizes the chains packing orthogonally to their axis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739479001029
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  • 4
    Electronic Resource
    Electronic Resource
    Odontoblast Differentiation of Human Dental Pulp Cells in Explant Cultures (2000)
    Springer
    Calcified tissue international 66 (2000), S. 129-138 
    Details
    ISSN: 1432-0827
    Keywords: Key words: Human — Tooth — Culture — Odontoblast — Mineralization.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. In order to elucidate the mechanisms involved in human dentin formation, we developed a cell culture system to promote differentiation of dental pulp cells into odontoblasts. Explants from human teeth were cultured in Eagle's basal medium supplemented with 10% or 15% fetal calf serum, with or without β-glycerophosphate (βGP). Addition of βGP to the culture medium induced odontoblast features in the cultured pulp cells. Cells polarized and some of them exhibited a typical cellular extension. In some cases, cells aligned with their processes oriented in the same direction and developed junctional complexes similar to the terminal web linking odontoblasts in vivo. Fine structural analyses showed the presence of typical intracellular organelles of the odontoblast body, whereas the process contained only cytoskeleton elements and secretory vesicles. Polarized cells deposited onto the plastic dishes an abundant and organized type I collagen-rich matrix with areas of mineralization appearing thereafter. X-ray microanalysis showed the presence of calcium and phosphorus and the electron diffraction pattern confirmed the apatitic crystal structure of the mineral. High expression of α1(l) collagen mRNAs was detected in all polarized cells whereas dentin sialoprotein gene was mainly expressed in mineralizing areas. This cell culture system allowed for the differentiation of pulp cells into odontoblasts, at both the morphological and functional level. Moreover, these cells presented a spatial organization similar to the odontoblastic layer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00005833
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  • 5
    Electronic Resource
    Electronic Resource
    Acellular Mineral Deposition in Collagen-Based Biomaterials Incubated in Cell Culture Media (2000)
    Springer
    Calcified tissue international 66 (2000), S. 204-211 
    Details
    ISSN: 1432-0827
    Keywords: Key words: Collagen — Calcification — Apatite — Chondroitin 4-sulfate — Tissue engineering.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. Rapid developments in tissue engineering have renewed interest in biodegradable three-dimensional structures such as collagen-based biomaterials. Collagen matrices seeded in vitro with fibroblasts, osteoblasts, and chondrocytes can form tissues resembling skin, bone, and cartilage that could be used as functional substitutes for damaged tissues. Collagen is associated with both dystrophic calcification of collagenous implants and bone mineralization. We report here the calcification properties of collagen sponges incubated in cell-free media. Mineral deposited in sponges was identified by X-ray and electron diffraction, Fourier transform infrared spectroscopy, and the molar ratio of calcium:phosphorus (Ca:P) as a poorly crystalline apatite similar to bone. The degree of calcification increased with length of incubation and the Ca and P content of the media, with 10–15% Ca (dry weight) after 21 days' incubation in media containing 1.6–3 mM Ca and a Ca × P molar product of 2–3 mM2, but only 2% Ca after incubation in medium with 1.33 mM Ca and a 1.7 mM2 Ca × P molar product. Mineral deposition was completely inhibited in sponges that were washed extensively and initially contained less than 0.01% P. Readdition of phosphate in these sponges and subsequent freeze drying and sterilization restore their mineralization capacity, suggesting that collagen per se cannot initiate calcification and that the inorganic phosphate content associated with the collagen preparation process is in the solid state a potential nucleator. Addition of chondroitin 4-sulfate to the sponges partially or totally inhibited mineral deposition, even though 80–90% of the compound was released within 24 hours. These results indicate that acellular calcification of collagen-based biomaterials can occur under the culture conditions currently used in tissue engineering.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002230010041
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  • 6
    Electronic Resource
    Electronic Resource
    Contrasted modes of amphibole development in coronitic metagabbros: a TEM investigation (1988)
    Springer
    Physics and chemistry of minerals 16 (1988), S. 130-139 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract A TEM investigation of amphibole development in granulitic metagabbros is presented. Three different sites of amphibole nucleation and growth are observed: (i) in the clinopyroxene-plagioclase interphase boundaries, corresponding to a reconstructive transformation involving intercrystalline diffusion; (ii) along pyroxene fractures, with competition between inter- and intracrystalline diffusion; (iii) within the pyroxene crystals, through a topotactic conversion, controlled by intracrystalline diffusion. These different reaction sites are studied in order to discuss some aspects of reaction mechanisms within undeformed metamorphic rocks, putting into balance intracrystalline versus intercrystalline processes. According to the possible paths (crystal lattice and its defects, fractures and mineral interfaces), contrasted amounts of reaction products, together with different amphibole compositions are evidenced. These results indicate that the diffusion rate of Al, Fe, Mg and OH is the rate controlling factor for amphibole-forming reaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00203196
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  • 7
    Electronic Resource
    Electronic Resource
    Isotactic poly(pentene-1): Form III (1976)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 1161-1167 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A new crystalline form of isotactic poly(pentene-1) was obtained from dilute solution in amyl acetate. We have designated it as form III. The morphology and structure of isothermally crystallized samples were investigated by electron microscopy and electron and x-ray diffraction. This crystalline modification can be indexed on an orthorhombic unit cell (cell dimensions: a = 21.20 ± 0.05 Å, b = 11.48 ± 0.05 Å, c = 14.39 ± 0.05 Å (fiber axis) and probable space group P212121).
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1976.180140701
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  • 8
    Electronic Resource
    Electronic Resource
    Isotactic poly(pentene-1): Polymorphism of form I (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 971-976 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The polymorphism of isotactic poly(pentene-1) form I was studied by x-ray diffraction. Upon quenching from the melt at a temperature below 25°C, the films crystallized in a stable monoclinic form, which we have designated as form I (a = 22.4 ± 0.2 Å, b = 6.49 ± 0.05 Å, c = 21.2 ± 0.2 Å, β = 91 ± 1°). For higher quenching temperatures, a metastable form, form I′, appeared, which transforms to the normal modification upon aging (monoclinic, with: a = 24.3 ± 0.2 Å, b = 6.50 ± 0.05 Å, c = 19.3 ± 0.2 Å, β = 96 ± 2°). Both modifications have a 31 helical conformation. Limited changes in the packing mode could explain this polymorphism.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.180160604
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