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  • 1975-1979  (30)
  • 1960-1964  (5)
  • 1930-1934
  • 1870-1879
  • 1830-1839
  • Polymer and Materials Science  (32)
  • Octacalcium phosphate  (3)
  • 1
    Electronic Resource
    Electronic Resource
    A thermodynamic analysis of the secondary transition in the spontaneous precipitation of calcium phosphate (1978)
    Springer
    Calcified tissue international 25 (1978), S. 209-216 
    Details
    ISSN: 1432-0827
    Keywords: Thermodynamics ; Kinetics ; Apatite ; Octacalcium phosphate ; Tricalcium phosphate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary A thermodynamic analysis has been made of the secondary transition stage in the spontaneous precipitation of calcium phosphate following the amorphous-crystalline transformation. The first formed crystalline material has a solubility similar to that of octacalcium phosphate (OCP) and the computed thermodynamic solubility product remains invariant in the pH range 7.00–8.60. The duration of the secondary stage is sensitive to pH and the transition appears to occur by hydrolysis of the first formed OCP-like phase to a more basic apatitic phase with a tricalcium phosphate (TCP) stoichiometry. The crystalline material at the end of this transition has an invariant solubility product, in the pH range 7.00 to 8.60, when the TCP-like molecular formula is assumed. Changes in the solution chemistry which accompany the solid-tosolid transitions are consistent with the above conclusions. The results of this study are also consistent with those of a previous study which suggest that the stability of the amorphous calcium phosphate phase is dependent upon the instability of the solution phase with respect to OCP formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02010771
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  • 2
    Electronic Resource
    Electronic Resource
    The maturation of crystalline calcium phosphates in aqueous suspensions at physiologic pH (1977)
    Springer
    Calcified tissue international 23 (1977), S. 259-269 
    Details
    ISSN: 1432-0827
    Keywords: Amorphous calcium phosphate ; Apatite ; Calcification ; Octacalcium phosphate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The maturation of calcium phosphate crystals formed by the conversion of spontaneously precipitated amorphous calcium phosphate (ACP) was studied in aqueous media at temperatures ranging from 20° to 37°. Reaction pH was kept at 7.4 with either Hepes buffer or by the pH-stat addition of base. Reaction kinetics were followed by monitoring solution calcium and total phosphate, and, in the pH-stat controlled reaction, by recording the amount of KOH needed to maintain pH. Reaction products were examined chemically and by X-ray diffraction and transmission electron microcopy. The first crystals to form deviated markedly from apatite in morphology, composition, structure, and solubility. They were extremely thin and flaky in appearance, had a low Ca/P molar ratio (1.4), contained an appreciable amount of acid phosphate (16%), and had an exceptionally largea-axis (10.5 Å vs. 9.4 Å for apatite). With maturation, the crystals became thicker but smaller in lateral dimensions, more apatitelike in structure and composition, and less soluble. However, this ripening of the crystals was accompanied by unusual inflections in the solution Ca and total PO4 curves, and, in the case of the pH-stat experiments, in the OH consumption profiles as well. These anomalous post-ACP solution changes suggest that a phase change had taken place during crystal maturation. Although the observed structural and compositional changes are not inconsistent with the perfection of an initially defective apatite, the changes in crystal morphology and the anomalous behavior of the reaction solution may more accurately reflect a conversion of the ACP first into an OCP-like crystalline phase which subsequently hydrolyzes into apatite.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02012795
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  • 3
    Electronic Resource
    Electronic Resource
    A thermodynamic analysis of the amorphous to crystalline calcium phosphate transformation (1978)
    Springer
    Calcified tissue international 25 (1978), S. 59-68 
    Details
    ISSN: 1432-0827
    Keywords: Amorphous calcium phosphate ; Thermodynamics ; Apatite ; Octacalcium phosphate ; Tricalcium phosphate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary A thermodynamic analysis of the precipitation of amorphous calcium phosphate (ACP) and its transformation to crystalline apatite has been made. A nearly constant ion product, over a wide variety of conditions, was obtained for a tricalcium phosphate (TCP)-like phase suggesting that the molecular unit which governs the solubility of ACP may be similar in composition to TCP. The introduction of 10% acid phosphate into the formula for the TCP ion product improves the fit of experimental data and results in an invariant ion product. The stability of ACP in solution was found to be dependent upon its thermodynamic instability with respect to an octacalcium phosphate (OCP)-like phase. The dependence of the induction period for the amorphous to crystalline transformation upon the pH and the Ca/P ratio of the solution is best explained by the assumption that an OCP-like phase is initially nucleated on the surfaces of the ACP particles. The events that occur in the immediate post-transition period suggest the hydrolysis of this OCP-like material to an apatitic phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02010752
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  • 4
    Electronic Resource
    Electronic Resource
    A method for measuring sedimentation and diffusion of macromolecules in capillary tubes by total intensity and quasi-elastic light-scattering techniquesPresented in part at the Symposium on New Generation Instrumentation in Rheology, Rheology Society, Cincinnati, Ohio, January 1973, by M. H. Birnboim. (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 419-430 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Light scattered from a macromolecular solution in a capillary tube is used to determine both the sedimentation and translational diffusion coefficients. The capillary tube is spun in a preparative centrifuge, removed, and placed in a light-scattering photometer equipped with a scanning mechanism. The intensity distribution of scattered light along the tube represents the concentration profile in the tube and provides the measure of boundary migration. The sedimentation coefficient is determined from this measure and the applied centrifugal field. The diffusion coefficient is obtained from a time-autocorrelation analysis of fluctuations in intensity of light scattered from any fixed point of the profile. These coefficients were obtained for two monodisperse systems, R17 bacteriophage and 28s ribosomal rat liver RNA. The molecular weights obtained from ratios of these coefficients are in good agreement with literature values. In the sedimentation analysis, deviations from linearity between boundary displacement and applied field were found to be less than 1%. This precision confirms that the boundary is stable for the capillary geometry even in the absence of a preformed density gradient. The sedimentation coefficients of identical samples were also measured with the Spinco Model E analytical ultracentrifuge; results of the two methods agree to within 4%.As a consequence of the capillary tube geometry and light-scattering detection, sedimentation coefficients can be obtained from sample volumes of less than 100 μl. This detection techniques is thus far demonstrated to be at least an order of magnitude more sensitive than Schlieren optics, thereby useful when uv absorption is not applicable. For diffusion measurements there are also several inherent advantages. The diffusion coefficient is obtained from the identical sample, and scanning provides the capability to measure D from various parts of the sedimentation profiles and thereby directly explore concentration dependence, homogeneity, and integrity of the sample. The capillary tube with a layer of silicone oil over the sample and centrifugation provides an effective method to cleanse the solution and trap all dust.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1975.360140214
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  • 5
    Electronic Resource
    Electronic Resource
    A contribution to the mechanism of the “four-center-type” photopolymerization (1977)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 178 (1977), S. 631-634 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1977.021780233
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  • 6
    Electronic Resource
    Electronic Resource
    Polymere mit dem Zentralatom eines makrocyclus in der hauptkette, 2.1. Mitteilung: cf.1. Polykondensationsreaktionen mit Germaniumkomplexen des Phthalocyanins und meso-Tetraphenylporphins (1975)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 176 (1975), S. 831-847 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Dihydroxy(phthalocyanino)germanium (1b) and Dihydroxy(tetraphenylporphino)germanium (3b) react with different monovalent alcohols to afford low-molecular bisalkoxyderivatives (1c-f and 3c-h). With bivalent alcohols and phenols polymers of the structure 5 and 6 or 8a, 9a and 8b, 9b, resp., are obtained.Dichloro(phthalocyanino)germanium (1a) and Dichlor(tetraphenylporphino)germanium (3a) react also with phenol, resp. hydroquinone, to give low-molecular and polymeric phenoxy-derivatives. The reaction of 1b and 3b with mono- and dibasic carboxylic acids leads to the corresponding esters.Dehydration of 3b gives polymeric porphin 15.The IR-spectra of the prepared compounds are discussed and compared with the analogous complexes of hemiporphyrazingermanium.Thermogravimetric and semiconductive measurements (σ298K = 10-10 - 10-15Ω-1 cm-1) are described.
    Notes: Dihydroxyphthalocyaningermanium (1b) und Dihydroxytetraphenylporphingermanium (3b) werden mit verschiedenen einwertigen Alkoholen zu den niedermolekularen Bisalkoxy-Derivaten (1c-f bzw. 3c-h) umgesetzt. Mit zweiwertigen Alkoholen und Phenolen können Polymere der Struktur 5 und 6 bzw. 8a, 9a und 8b, 9b erhalten werden.Dichlorphthalocyaningermanium (1a) und Dichlortetraphenylporphingermanium (3a) reagieren mit Phenol bzw. Hydrochinon ebenfalls zu niedermolekularen und polymeren Phenoxy-Derivaten. Die Umsetzung von 1b und 3b mit ein- und zweibasischen Carbonsäuren führt zu den entsprechenden Estern.Durch Dehydratisierung von 3b kann das polymere Porphin 15 hergestellt werden.Die IR-Spektren der dargestellten Verbindungen werden im Vergleich zu den analogen Hemiporphyrazingermaniumkomplexen diskutiert. Thermogravimetrische und Halbleitermessungen (σ298 K = 10-10 - 10-15Ω-1 cm-1) werden beschrieben.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1975.021760401
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  • 7
    Electronic Resource
    Electronic Resource
    Polymere mit dem zentralatom eines makrocyclus in der hauptkette, 3.2. Mitteilung: cf.2.Polykondensationsreaktionen mit zinnkomplexen des meso-tetraphenylporphins, phthalocyanins und hemiporphyrazins (1975)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 176 (1975), S. 1919-1927 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Dihydroxy(meso-tetraphenylporphino)tin (1b), dihydroxy(phthalocyanino)tin (1d), and dihydroxy(hemiporphyrazino)tin (1f) react with bivalent phenols to afford polymers of type B. With 1,2-ethanediol and 1b low molecular compound 3 is obtained, which eliminates 1,2-ethanediol to give poly[oxyethyleneoxy(meso-tetraphenylporphin)stannandiyl] (4). Dehydration of the dihydroxy compounds 1b, 1d, 1f leads to polymers of type C. The IR-spectra of the prepared compounds are discussed; thermogravimetric and semiconductive measurements (σ298K≈10-6-10-16Ω-1cm-1) are described and compared with the analogous complexes of germanium.
    Notes: Dihydroxy-meso-tetraphenylporphinzinn (1b), Dihydroxyphthalocyaninzinn (1d) und Dihydroxyhemiporphyrazinzinn (1f) reagieren mit zweiwertigen Phenolen zu Polymeren des Typs B. Aus Äthylenglykol und 1b läßt sich die niedermolekulare Verbindung 3 erhalten, die unter Äthylenglykolabspaltung Poly[oxyäthylenoxy(meso-tetraphenylporphin)stannandiyl] (4) ergibt.Durch Dehydratation der Dihydroxy-Verbindungen 1b, 1d, 1f lassen sich Polymere des Typs C synthetisieren.Die IR-Spektren der dargestellten Verbindungen werden diskutiert; thermogravimetrische und Halbleitermessungen (σ298K≈10-6-10-16Ω-1cm-1) werden beschrieben und mit den analogen Germaniumverbindungen verglichen.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1975.021760702
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  • 8
    Electronic Resource
    Electronic Resource
    Compatibility of ABA poly(styrene-b-isoprene)/poly(2,6-dimethylphenylene oxide) blends (1978)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 22 (1978), S. 719-725 
    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: A variety of blends of ABA poly(styrene-b-isoprene) copolymers with poly(2,6-dimethylphenylene oxide) were prepared. Their compatibility was examined by measuring both the apparent modulus of rigidity and the loss tangent. Several blends showed a unique glass transition temperature between those of the individual components, which indicated compatibility. It was found that only those copolymers which phase separate are compatible with poly(2,6-dimethylphenylene oxide).
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1978.070220312
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  • 9
    Electronic Resource
    Electronic Resource
    Zur Vermeidung von dynamischen Kraftmeßfehlern bei Neigungspendel-Kraftmeßeinrichtungen (1979)
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 10 (1979), S. 449-455 
    Details
    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
    Description / Table of Contents: The Prevention of Inertial Force Measurement Inaccuracies Encountered in Pendulum-type DynamometersTest machines, which are equipped with a force measuring device utilizing the inclining pendulum, are subject to dynamic measurement inaccuracies due to the inertia of the pendulum.The initial discussion demonstrates that the dynamic inaccuracy of measurement encountered with test machines using an inclining pendulum - force measurement device can only be calculated for the complete test machine/test piece configuration. With reference to the results of experiments, it will be proved that, as with the experiments carried out by Kravcenko, the indicated dynamic force and the dynamic force in the testpiece are antiphase and unequal.Additionally it will be shown that, through the experiment results, the equation from Schultze/Baumann for the permissible rate of test is confirmed only in the interpretation from Kravcenko.Further equations concerning the limitations of the rate of test are shown and their relevant fields of applications are discussed. Finally, factors are presented which stipulate a reduction of the permissible rate of test or permit an increase in this rate, dependent upon the force-elongation characteristic of the test piece and the measured variable under consideration.
    Notes: An Prüfmaschinen, welche Kraftmeßeinrichtungen mit Neigungspendeln besitzen, treten durch die Trägheit des Pendels dynamische Meßfehler auf.Es wird zunächst klargestellt, daß die dynamischen Meßfehler bei Prüfmaschinen mit Neigungspendel-Kraftmeßeinrichtungen nur für das Gesamtsystem Prüfmaschine/Probe berechnet werden können.Anhand von Versuchsergebnissen wird nachgewiesen, daß - entsprechend Untersuchungen von Kravčko - die angezeigte dynamische Kraft und die dynamische Probenkraft gegenphasig und ungleich sind. Außerdem wird gezeigt, daß durch die Versuchsergebnisse die Gleichg. von Schultze/Baumann für die zulässige Prüfgeschwindigkeit nur in der Deutung von Kravčko bestätigt wird.Weitere Gleichungen für Die Begrenzung der Prüfgeschwindigkeit wer den angegeben und ihr Einsatzbereich besprochen. Schließlich werden Faktoren angegeben, die je nach dem Kraft-Verlängerungs-Verhalten der Probe und je nach der gesuchten Meßgröße eine Verringerung der zulässigen Prüfgeschwindigkeit bedingen oder eine Vergrößerung der selben zulassen.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mawe.19790101209
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  • 10
    Electronic Resource
    Electronic Resource
    Über das Flammspritzen von AluminiumoxydGekürzte Fassung der von der Fakultät für Bergbau und Hüttenwesen der Bergakademie Clausthal-Zellerfeld genehmigten Dissertationsarbeit. (1960)
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 11 (1960), S. 601-616 
    Details
    ISSN: 0947-5117
    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
    Description / Table of Contents: Flame spraying of aluminaCeramic coatings produced by the flame spraying process are intended to protect the basic material against corrosion, erosion and oxidation as well as to act as a thermal barrier. For this purpose, alumina was found to be particularly well suited because of its high melting point, hardness, chemical resistance and other favourable properties. With this material as a model substance, the basic processes encountered with the spraying of ceramic powders have been investigated. The investigations comprised the melting process in the flame jet, the composition, lattice structure and physical properties of the spray coating, and the adhesion of the latter on pure metals and alloys with different surface roughness conditions.Although the porosity of these coatings is small, it prevents them from offering complete protection against corrosion and oxidation. But the protection effect can be enhanced by using resistant intermediate metal or enamel layers, and by stabilizing the sprayed coating. Owing to their high abrasion resistance and thermal barrier effect, these coatings have already found a wide field of application.
    Notes: Nach dem Flammspritzverfahren hergestellte keramische Überzüge haben die Aufgabe, das Grundmaterial gegen Korrosion, Erosion and Oxydation zu schützen sowie als Wärmeschranke zu wirken. Besonders geeignet erweist sich hierfür Aluminiumoxyd wegen seines hohen Schmelzpunktes, seiner Härte, seiner chemischen Resistenz und anderer günstiger Eigenschaften. Mit diesem Material als Modellsubstanz wurden die grundlegenden Vorgänge beim Spritzen von Keramik-Pulvern verfolgt. Die Untersuchungen erstreckten sich auf den Schmelzvorgang im Flammstrahl, auf den Aufbau, die Gitterstruktur und die physikalischen Eigenschaften der Spritzschicht sowie auf deren Haftung auf Reinmetallen und Legierungen mit verschiedener Oberflächenaufrauhung.Die Überzüge bieten wegen ihrer, wenn auch geringen Porosität keinen vollständigen Schutz gegen Korrosion und Oxydation. Durch Verwendung von resistenten Zwischenschichten aus Metall oder Email und durch Stabilisierung der Spritzschicht kann die Schutzwirkung jedoch erhöht werden. Auf Grund ihrer Abriebfestigkeit und ihrer wärmedämmenden Wirkung haben die Überzüge bereits ein weites Anwendungsgebiet gefunden.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/maco.19600111002
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