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  • 1
    ISSN: 1432-0827
    Keywords: Na, Mg, and CO3 ; Carbonated apatite ; Tooth enamel ; IR spectrum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Apatites containing Na, Mg, and CO3 in amounts occurring in tooth enamel mineral were synthesized by precipitation from aqueous solutions. The X-ray diffraction patterns showed only apatitic reflections, which were somewhat broader than those of enamel. X-ray Guinier photographs resulted in diffuse reflections from which the lattice parameters could not be determined. The infrared (IR) absorption spectrum of the synthetic samples was practically identical with that of tooth enamel. However, after heating the samples for 1/2 h at a temperature between 300 and 600°C, no absorption peak was found at 2340 cm−1 as in the IR spectrum of tooth enamel after heating.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Solid State Ionics 16 (1985), S. 105-112 
    ISSN: 0167-2738
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0827
    Keywords: Calcium hydroxyapatite ; Lead hydroxyapatite ; Cation distribution ; Lattice parameters ; Solid solutions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Solid solutions of calcium hydroxyapatite (CaOHA) and lead hydroxyapatite (PbOHA) of the formula Ca10−x Pbx (PO4)6 (OH)2 were prepared by coprecipitation followed by heating at 800°C in a stream of CO2-free water vapor of 1 atm. The samples were apatitic in the range 0〈x〈6 and contained lead phosphates as a second phase at higher Pb/Ca ratios. Lattice parameters and cation distribution of the apatitic samples were determined by X-ray diffraction. The lattice parameters varied linearly with x in the range considered, whereas all Pb2+ were located in the sixfold position for cations. There was a miscibility gap in the apatite series of solid solutions in the range 1〈x〈4, whereas apatites in the range 6〈x〈10 were not stable under the conditions of preparation. It is concluded that apatites in the range 4〈x〈6 represent a minimum in the free energy of solid solutions between CaOHA and PbOHA.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 29 (1979), S. 127-131 
    ISSN: 1432-0827
    Keywords: Calcium hydroxyapatite ; Strontium hydroxyapatite ; Cation distribution ; Lattice parameters ; Solid solutions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Solid solutions of strontium and calcium hydroxyapatite were synthesized by solid-state reaction. Lattice parameters of these compounds were determined using two types of Guinier cameras. They vary linearly with the molar percentage of strontium hydroxyapatite. The distribution of Ca and Sr ions over the fourfold and sixfold positions in the apatite structure was determined by comparing experimental and calculated values for the intensity ratios of suitable reflections. A slight, although significant, preference of Sr for the sixfold position was found. An ideal behavior is predicted for these solid solutions.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 13 (1984), S. 91-97 
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A computer program based on the use of Gaussian expressions for the x-ray distribution with depth [φ(ρz)curves] was tested on its usefulness for quantitative electron probe microanalysis. As the good results originally claimed for a similar program could not be reproduced initially, it was subjected to a detailed analysis. As a result, some modifications in the approach are proposed. Apart from increasing the speed of calculation considerably, the modified expressions provide a better insight into the delicate balance which has to exit between the relevant quantities involved. After a new optimization process the modified program was tested on about 450 published microanalyses. The results show that the φ(ρz) approach is indeed very promising as a narrow histogram with an r. m. s. value of 5. 4% could be produced. Finally, some suggestions are made for future improvements.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 15 (1986), S. 135-141 
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Introductory investigations performed in order to make quantitative electron-probe microanalysis of very light elements such as boron, carbon, nitrogen or oxygen possible are described. The practical problems encountered in this kind of work are discussed in detail and, where possible, solutions are proposed. It is shown that with very light elements such as carbon it is no longer permitted to measure x-ray intensities at the position of the maximum of the emission peak as the shape of the carbon Kα peak is subject to strong alterations, depending on the type of chemical bond involved. As a consequence, integral measurements have to be performed and it is shown that errors of 30-50% can easily be made if this is neglected. The lengthy procedures, connected with integral intensity measurements, can be shortened considerably by the introduction of area/peak factors, which, by definition, represent the ratio between the correct area (integral) and the peak intensity ratio. The accurate determination of such factors for 13 binary carbides is described. This set of factors will permit future measurements simply on the peak; multiplication of the peak intensity ratio by the appropriate area/peak factors will then yield the correct integral intensity ratios.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 15 (1986), S. 143-150 
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The performances of four current matrix correction programs have been tested on a data file of measurements on 13 binary carbides between 4 and 30 kV. Both the metal lines as well as the carbon Kα line have been measured, which resulted in 145 k ratios for the metals (relative to elemental standards) and 117 integral k ratios for carbon Kα (relative to Fe3C).Evidence is presented that the existing sets of mass absorption coefficients for carbon Kα radiation are perhaps not fully consistent and a new set is therefore proposed, which is in better agreement with the experimental results. Finally, it is shown that the modified Gaussian φ(ρz) approach, when used in conjunction with the new set of mass absorption coefficients, leads to unexpectedly good results, with a relative root-mean-square value of 3.7%. This demonstrates that even for carbon very good accuracy can be obtained, provided that proper care is exercised in the measurements and the proper procedures are followed.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 21 (1990), S. 90-92 
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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