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  • 1
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 361-363 (Nov. 2007), p. 1237-1240 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Apatite/β−TCP particles exhibiting non-conventional urchin-like morphology wereprepared by hydrothermal synthesis. Their implantation in the rat calvarium was followed during 60days. A total absence of osteoconduction was observed despite a favorable chemical composition,stressing the fundamental role of particle morphology on bone regeneration. Results are discussedin relation with other literature data. Possible explanations include the disfavored accumulation ofbiological mediators due to the acicular shape of the particles and/or a limited accessibility for cells
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 361-363 (Nov. 2007), p. 79-82 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The interaction of calcium phosphates with biological molecules under controlledconditions permits the formulation of meaningful conclusions concerning the driving forces. Theuptake and release at the material-solution interface is the result of the various interactions betweenand within the system components which include the solid surface, the adsorbate, the solvent andother solutes present. The understanding of adsorption and desorption mechanisms with respect toactive molecules can be exploited for the development of drug delivery applications
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 396-398 (Oct. 2008), p. 225-228 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The purpose of this study was to improve injectability and cohesiveness of original calcium carbonate-calcium phosphate mixed (CaCO3-CaP) self-setting paste for bone filling and repair. With this aim in view dry co-grinding was implemented on the solid phase (vaterite and dicalcium phosphate dihydrate) of this cement. A protocol designed to quantify paste injectability has been established and pointed out the synergistic positive effects of solid phase co-grinding treatment on injectability, cohesiveness and setting time of the paste. The improvement of these properties are related to close and homogeneous association of reactive powders and to the decrease of specific surface area favoring the powders hydration process enhancing setting reaction rate. In addition, the particle size decrease and morphology modification improved flowability of the paste which results in a low and constant (320 g) force level to extrude the paste
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  • 4
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Advances in science and technology Vol. 49 (Oct. 2006), p. 45-50 
    ISSN: 1662-0356
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Natural Sciences in General , Technology
    Notes: Calcium phosphates (Ca-P) are major constituents of calcified tissues, and are alsoextensively used for the elaboration of biomaterials. However, the usual high-temperature sinteringprocesses generally lead to strong alterations of their chemical, physical and biological properties.Spark plasma sintering (SPS) is a non-conventional sintering technique based on the use of pulsedcurrent, enabling fast heating and cooling rates, and lower sintering temperatures are oftenobserved. The sintering of several orthophosphates (DCPD, amorphous TCP, beta-TCP, OCP, HAand biomimetic nanocrystalline apatites) by SPS was investigated in order to track potentialadvantages of this technique over usual Ca-P sintering methods. Special attention was given to theSPS consolidation of highly bioactive nanocrystalline apatites
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  • 5
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Advances in science and technology Vol. 49 (Oct. 2006), p. 27-36 
    ISSN: 1662-0356
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Natural Sciences in General , Technology
    Notes: Apatites can accommodate a large number of vacancies and afford multiple ionicsubstitutions determining their reactivity and biological properties. Unlike other biominerals theyoffer a unique adaptability to various biological functions. The diversity of apatites is essentiallyrelated to their structure and to their mode of formation. Special charge compensation mechanismsallow molecular insertions and ion substitutions and determine to some extent their solubilitybehaviour. Apatite formation at physiological pH involves a structured surface hydrated layernourishing the development of apatite domains. This surface layer contains relatively mobile andexchangeable ions, and is mainly responsible for the surface properties of apatite crystals from achemical (dissolution properties, ion exchange ability, ion insertions, molecule adsorption andinsertions) and a physical (surface charge, interfacial energy) point of view. These characteristicsare used by living organisms and can also be exploited in material science
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Numerical algorithms 17 (1998), S. 279-311 
    ISSN: 1572-9265
    Keywords: conjugate gradient ; Ritz values ; superlinear convergence ; Rayleigh matrix ; Krylov subspaces ; series of linear problems ; 65B99 ; 65Y05
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract The approximation to the solution of large sparse symmetric linear problems arising from nonlinear systems of equations is considered. We are focusing herein on reusing information from previous processes while solving a succession of linear problems with a Conjugate Gradient algorithm. We present a new Rayleigh–Ritz preconditioner that is based on the Krylov subspaces and superconvergence properties, and consists of a suitable reuse of a given set of Ritz vectors. The relevance and the mathematical foundations of the current approach are detailed and the construction of the preconditioner is presented either for the unconstrained or the constrained problems. A corresponding practical preconditioner for iterative domain decomposition methods applied to nonlinear elasticity is addressed, and numerical validation is performed on a poorly-conditioned large-scale practical problem.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Numerical algorithms 23 (2000), S. 1-30 
    ISSN: 1572-9265
    Keywords: iterative approach ; conjugate gradient ; Krylov subspaces ; superconvergence ; Ritz values ; nonlinear optimization ; parallel supercomputing ; 65B99 ; 65Y05
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract Discrete solution to nonlinear systems problems that leads to a series of linear problems associated with non-invariant large-scale sparse symmetric positive matrices is herein considered. Each linear problem is solved iteratively by a conjugate gradient method. We introduce in this paper new solvers (IRKS, GIRKS and D-GIRKS) that rely on an iterative reuse of Krylov subspaces associated with previously solved linear problems. Numerical assessments are provided on large-scale engineering applications. Considerations related to parallel supercomputing are also addressed.
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  • 8
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 37 (1997), S. 508-516 
    ISSN: 0021-9304
    Keywords: osteogenesis ; proliferation ; differentiation ; osteoblast ; human ; hydroxyapatite ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: In order to evaluate whether human osteoblastic cells differentiate normally on hydroxyapatite, we have compared the adhesion, proliferation, and differentiation of human trabecular (HT) osteoblastic cells on synthetic-dense hydroxyapatite and on standard plastic culture. We show here that initial HT cell attachment was 4-fold lower on hydroxyapatite than on plastic after 4 h of culture, and that normal cell attachment on hydroxyapatite was restored after 18 h of culture. HT cell proliferation was similar on the two substrates at 2-8 days of culture, but was lower on hydroxyapatite compared to plastic after 15 and 28 days of culture, as evaluated by DNA synthesis or cell number. HT cells cultured on both substrates produced an abundant extracellular matrix which immunostained for Type I collagen. The levels of carboxyterminal propeptide of Type I procollagen (P1CP) in the medium were lower in HT cell cultures on hydroxyapatite than on plastic. In addition, (3H)-proline incorporation into matrix proteins and the mean thickness of matrix layers were 52% and 26% lower, respectively, on hydroxyapatite compared to plastic after 4 weeks of culture, indicating that the total collagenous matrix synthesized by HT cells was lower on hydroxyapatite. However, (3H)-proline and calcium uptake expressed per cell was higher on hydroxyapatite than on plastic. The results show that human osteoblastic cells attach, proliferate, and differentiate on dense hydroxyapatite with a sequence similar to that of plastic. However, the growth of human osteoblastic cells is lower on hydroxyapatite in long-term culture, which results in a reduced amount of extracellular matrix, although matrix production per cell may be increased. © 1997 John Wiley & Sons, Inc. J Biomed Mater Res, 37, 508-516, 1997.
    Additional Material: 6 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 43 (1998), S. 399-409 
    ISSN: 0021-9304
    Keywords: amorphous calcium phosphate ; bone substitute ; bone graft ; hydroxyapatite ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The in vitro and in vivo properties of a novel, fully resorbable, apatitic calcium phosphate bone substitute (ABS) are described. The ABS was prepared from calcium phosphate precursors that were hydrated to form an injectable paste that hardens endothermically at 37 °C to form a poorly crystalline apatitic calcium phosphate (PCA). The PCA reaction product is stable in vivo as determined by FTIR and XRD analysis of rabbit intramuscular implants of ABS retrieved 4, 7, and 14 days postimplantation. Bone formation and resorption characteristics of the ABS material were characterized in a canine femoral slot defect model. Femoral slot defects in dogs were filled with either autologous bone implants or the ABS material. Sections of femoral bone defect site from animals sacrificed at 3, 4, 12, 26, and 52 weeks demonstrated that new bone formation proceeded similarly in both autograft and ABS filled slots. Defects receiving either material were filled with trabecular bone in the first 3 to 4 weeks after implantation; lamellar or cortical bone formation was well established by week 12. New bone formation in ABS filled defects followed a time course comparable to autologous bone graft filled defects. Histomorphometric evaluation of ABS resorption and new bone formation indicated that the ABS material was greater than 99% resorbed within 26 weeks; residual ABS occupied 0.36 ± 0.36% (SEM, n = 4) of the original defect area at 26 weeks. Quantitatively and qualitatively, the autograft and ABS were associated with similar new bone growth and defect filling characteristics. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 43: 399-409, 1998
    Additional Material: 8 Ill.
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  • 10
    Publication Date: 2015-11-16
    Print ISSN: 1742-6588
    Electronic ISSN: 1742-6596
    Topics: Physics
    Published by Institute of Physics
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