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  • 1
    Electronic Resource
    Electronic Resource
    Diffusion of45Ca in bovine enamel (1977)
    Springer
    Calcified tissue international 24 (1977), S. 59-64 
    Details
    ISSN: 1432-0827
    Keywords: Enamel ; Calcium ; Exchange ; Diffusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The penetration of45Ca ions into whole bovine enamel from an aqueous solution was studied as a function of the Ca content in the solution. A sectioning technique was employed to measure the penetration of45Ca into the enamel. Probably only Ca ions occupying surface positions in the hydroxyapatite crystallites participate in the exchange process at the solution-enamel interface. The fraction of Ca ions participating in the exchange was 2% of the total number of Ca ions. Two different diffusion processes occur; firstly, a process governed by a diffusion coefficient, D1 ranging from about 5×10−14 to 2×10−12 cm2/s and strongly dependent on the calcium concentration in the solutions; and secondly a process with a concentration-independent diffusion coefficient, D2, with a value of 2.8×10−12 cm2/s. It is assumed that the 2 diffusion types correspond to intra-and interprismatic transport, respectively. A model based on the pore structure of dental enamel and on surface charges on hydroxyapatite crystallites is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02223297
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  • 2
    Electronic Resource
    Electronic Resource
    The temperature dependency of45Ca diffusion in bovine enamel (1977)
    Springer
    Calcified tissue international 24 (1977), S. 173-177 
    Details
    ISSN: 1432-0827
    Keywords: Enamel ; Calcium ; Diffusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The diffusion of45Ca ions in sound bovine enamel at pH 7.0 was studied as a function of temperature in the range 20°–40°C. The experimental data show that the diffusion is governed by two processes with activation energies of about 0.7 and 1.3 eV respectively. These values are considerably larger than the activation energy of calcium ion diffusion in water (0.2 eV). The diffusion process with the activation energy of 1.3 eV is dependent upon the calcium concentration in solution. A model based on the complex pore structure of enamel and on interactions of diffusing ions with the enamel constituents is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02223312
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Einbau von15N-Glyzin in VLDL und LDL: In-vivo-Synthese von Apolipoprotein B beim Menschen postabsorptiv und im Fastenzustand (1989)
    Springer
    Journal of molecular medicine 67 (1989), S. 280-285 
    Details
    ISSN: 1432-1440
    Keywords: 15N-Glycine ; Apolipoprotein-B-Synthesis ; Low density lipoprotein ; Very low density lipoprotein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In vivo synthesis of apolipoprotein B 100 (ApoB) was recently determined in man using stable isotopes. With this procedure we analyzed (1) the effect of fasting on synthesis of ApoB from very low density lipoprotein (VLDL) and (2) tracer enrichment in low density lipoprotein (LDL). After a 36-hour fasting period and in the post-absorptive state 4 healthy subjects were given a priming dose (8.7 µmol/kg) of15N glycine followed by a constant infusion (10 µmol/kg/h for 8 h) to achieve 5% tracer enrichment in the plasma pool of glycine. The K-values, i.e. fractional synthetic rates/hr of ApoB from VLDL were 0.53±0.26 vs. 0.43±0.16 (p〉0.05). Tracer enrichment in ApoB from LDL at the end of the infusions was 0.19% vs. 1.46% in ApoB from VLDL. The results indicate that (1) in young healthy postabsorptive individuals about 40% of ApoB from VLDL in plasma is synthesized per hour, (2) fasting does not materially affect fractional ApoB synthesis and (3) at 5%15N enrichment in plasma glycine, tracer enrichment in ApoB from LDL is at the lower limit of detection for the procedure employed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01892895
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  • 4
    Electronic Resource
    Electronic Resource
    Fissure sealants (1974)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 18 (1974), S. 2935-2944 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The adhesive bonding of a fast-setting system consisting of three different monomers to etched human enamel surfaces was investigated. Combinations of MMA, methacrylic acid, and adducts of glycidyl methacrylate and p-substituted phenols have been employed. Best results were obtained with hydrogen or t-butyl-substituted phenols. It is shown that a well-chosen three-component system has the advantage of a very low initial viscosity and fast setup times over two-component systems. Various compositions of three-component systems were studied. The maximum bond strength between enamel surfaces and the polymer was 80 kg/cm2. Setup times as well as in vivo setup times are reported.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1974.070181007
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  • 5
    Electronic Resource
    Electronic Resource
    Interaction of fibroblasts and polymer surfaces: relationship between surface free energy and fibroblast spreading (1983)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 17 (1983), S. 807-817 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Cell spreading and cell division rates of a transformed line of mouse lung fibroblasts were studied on various polymer surfaces in the presence of serum proteins. The bare polymer surfaces, as well as the protein-coated surfaces, were characterized by their polar (γsp) and dispersion (γsd) surface free energies. Cell spreading appeared to be dependent on the polar surface free energy. Cell spreading is low when the γsp of the bare surface is lower than 5 erg cm-2; marked spreading occurs when γsp is higher than 15 erg cm-2. A similar relationship was found between cell spreading and polarity of the protein-coated surfaces, although less pronounced than for the bare surfaces. Cell spreading appeared independent of the dispersion surface free energy. Cell division rate was the same on all surfaces tested.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820170508
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  • 6
    Electronic Resource
    Electronic Resource
    Dispersion and polar surface free energies of human enamel (1983)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 17 (1983), S. 637-641 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: In this study, the dispersion (γsd) and polar (γsp) surface free energies of human enamel with and without an acquired enamel pellicle and of crystalline hydroxyapatite were determined from contact angle measurements. The results show that γsp is strongly influenced by the presence of a pellicle; the total surface free energy (γs) is considerably smaller for enamel with an acquired pellicle than for enamel without an acquired pellicle. Enamel without an acquired enamel pellicle shows surface free energies comparable with those of crystalline hydroxyapatite.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820170408
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  • 7
    Electronic Resource
    Electronic Resource
    The influence of substratum surface free energy on growth and spreading of human fibroblasts in the presence and absence of serum proteins (1986)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 20 (1986), S. 773-784 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: To determine whether the surface free energy of polymer materials influences the spreading and growth of cells, surface free energies of 13 polymers and glass were related to spreading and growth of human skin fibroblasts. Experiments were performed in both the presence and absence of serum proteins. We calculated the surface free energy from contact angles of phosphate-buffered saline (PBS), n-propanol/PBS mixtures, and α-bromonaphthalene on the polymers, using the concept of polar and dispersion components accounting for spreading pressures. Cell spreading and substratum surface free energy (γs) showed a characteristic sigmoid relationship both in the presence and in the absence of serum proteins; good spreading only occurred when γs was higher than approximately 57 erg · cm-2. In the presence of serum proteins, cell spreading is similar on most materials; only few materials show relatively high cell spreading. Cell growth in the presence of serum proteins did not differ significantly on the various polymers with reference to their γs values. In contrast, two groups of polymers could be distinguished in the absence of serum with respect to cell growth. The first group showed increasing γs, whereas the second group showed consistently low cell growth. The results demonstrate the complex relationship between cell spreading and substratum surface free energy as well as the role of serum proteins in modifying the surface characteristics of polymers in relation to cell spreading and growth.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820200609
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  • 8
    Electronic Resource
    Electronic Resource
    Calculation of the Raman line broadening on carbonation in synthetic hydroxyapatite (1988)
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 19 (1988), S. 13-21 
    Details
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The position and broadening of the Raman band associated with the phosphate symmetric stretching vibration in hydroxyapatite are simulated using a simple inter- and intra-ionic potential. The results are compared with experimental values. This comparison was made as a function of the incorporation of carbonate ions in the lattice for a number of substitution models. The line width of the phosphate symmetric stretching vibration is shown both theoretically and experimentally to be dependent on the carbonate content. Good agreement between calculations and experiment is obtained. The results of the calculations offer some support to the suggestions in the literature that the dielectric constant has to be considered as a function of the distance in the lattice, increasing beyond the first environmental layer.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jrs.1250190104
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