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  • 1
    Electronic Resource
    Electronic Resource
    Biological bleaching of water-soluble coal macromolecules by a basidiomycete strain (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 95-101 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract There is need for new effective technologies to convert coal into environmentally acceptable liquid fuels. Thermochemical coal-conversion processes occur under extreme conditions. Thus there is a potential to use the biotransformation of coal as a cheap alternative method. A basidiomycete strain, which decomposes coal macromolecules, was isolated from humic-acid-rich soil of a lignite surface-mining region. The isolate showed the ability to decolorize liquid dark-brown media containing water-soluble coal-derived substances (humic acids). The presence of an easily available substrate is necessary for the biodegradation. The influence of different culture conditions on the bleaching effect was studied. Evidence for decomposition of water-soluble coal substances was provided by measuring the decrease of absorbance and the modification in the distribution of molecular masses. The degradation process resulted in a complete decolorization of the coal-derived humic acids and was also combined with massive alterations in their molecular structure. Solid-state #13C-NMR spectroscopy showed an increase of carboxylic groups as well as hydroxylated and methoxylated aliphatic groups, which indicates an oxidative attack. Enzymatic analysis showed the presence of a Mn peroxidase in the culture supernatant. Extracellular lignin peroxidase and laccase activities were not detectable. The production of the peroxidase was induced by addition of humic acids. But, in vitro, this enzyme did not cause a decolorization or reduction in molecular mass of the coal-derived humic acids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530050895
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  • 2
    Electronic Resource
    Electronic Resource
    Al2O3 against Al2O3 combination in hip endoprostheses. Histologic investigations with semiquantitative grading of revision and autopsy cases and abrasion measures (1994)
    Springer
    Journal of materials science 5 (1994), S. 657-661 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: For comparison of hip endoprostheses with Al2O3 combinations of the gliding surfaces with other material combinations, pseudocapsules and soft tissue membranes around hip endoprostheses retrieved at revision surgery or at autopsy were histologically investigated. In all tissue specimens around loosened prostheses, ceramic wear particles were found, in 50% of cases high-grade ceramic wear was seen. In contrast, only half of the autopsy cases revealed ceramic wear. Cases with Al2O3−Al2O3 combinations showed less villous transformation of the synovial tissue, a thinner synovial layer and reduced necroses in comparison to Al2O3-polyethylene and metal-polyethylene combinations. These differences appeared more pronounced in the autopsy cases. The result of this study confirm the hypothesis, that a high ceramic wear rate in loosened prostheses develops mainly as a consequence of loosening. For that reason, biologically fixation of implants with spongious structured surfaces and without bone cement fixation seems a logical consequence. Modular systems are necessary not only for stem and ball, but also for the acetabular component of the hip endoprostheses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00120351
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  • 3
    Electronic Resource
    Electronic Resource
    Investigations into the mechanical reliability of ceramic femoral heads for hip joints (1994)
    Springer
    Journal of materials science 5 (1994), S. 503-506 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: This paper reports the findings of a finite element analysis applied to the study of ceramic femoral ball heads. The objective of carrying out these analyses was to assess the shape design and loading conditions applied to specific femoral heads and to capture the stress fields developed when they are subjected to idealized test conditions. Two designs were considered, these being the existing Biolox keyhole shape, manufactured by Cerasiv, Medical Products Division and an alternative design with a flat top internal hole. For each of these designs, three load cases and two types of frictional contact were considered. It is shown that the key hole shape with full taper contact conditions together with the higher value of surface friction produce the lowest tensile stress fields in the ball head hence increasing mechanical reliability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00058992
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  • 4
    Electronic Resource
    Electronic Resource
    The colour of medical-grade zirconia (Y-TZP) (1996)
    Springer
    Journal of materials science 7 (1996), S. 559-565 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Optical spectroscopy, ESR spectroscopy, and standard and wavelength- and-temperature-resolved thermoluminenscence spectroscopy of as-sintered and γ-irradiated medical-grade yttrium-stabilized tetragonal zirconia polycrystal (Y-TZP) material showed that the pronounced colour change, after irradiation, from off-white to a purplish-grey shade can be related to two electronic transitions at local defects in the crystal lattice. The first transition could be associated with an electron-hole state characterized by an oxygen ion trapped in the vicinity of a yttrium ion (Y'ZrO*) and can be correlated with an optical absorption band at 2.6 eV (480 nm). The second transition is presumably an extrinsic defect correlated with an optical absorption band at 3.2 eV (395 nm). From the experimental results it can be concluded that those local electronic defects responsible for the colour change on γ-irradiation do not influence safety-related mechanical or chemical properties of the ceramic femoral ball heads of hip endoprostheses produced from Y-TZP.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00122179
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  • 5
    Electronic Resource
    Electronic Resource
    A systematic error in the temperature determination of a DTA effect by using the onset point (1975)
    Springer
    Journal of thermal analysis and calorimetry 8 (1975), S. 597-600 
    Details
    ISSN: 1572-8943
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The Committee on Standardization of the ICTA proposed a method for determination of the temperature of a DTA effect. This procedure is easy to perform, but leads to a systematic deviation from the true value. It is demonstrated that this deviation depends on the heating or cooling rate and the thermal conductivity of the sample.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01910140
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  • 6
    Electronic Resource
    Electronic Resource
    Ermüdungsverhalten von SiSiC (1982)
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 13 (1982), S. 355-360 
    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 Fatigue Behavior of SiSiCFor design purposes the engineering property datas especially the fatigue behavior of silicon carbide (SiSiC) were determined. Using linear elastic fracture mechanics the datas for slip casted and extruded SiSiC-samples were measured at room temperature. The correlation between stress, probability of failure, and time is shown in SPT-diagrams.
    Notes: Auf der Basis der Theorie der linear-elastischen Bruchmechanik wird die für die Konstruktion benötigte, zeitabhängige mechanische Festigkeit (Ermüdung) von stranggepreßtem und schlickergegossenem Siliziumcarbid (SiSiC) bei Raumtemperatur bestimmt.Der Zusammenhang zwischen Belastungshöhe, Ausfallswahrscheinlichkeit und Zeit wird in Form von SPT-Diagrammen dargestellt.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mawe.19820131006
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  • 7
    Electronic Resource
    Electronic Resource
    Diffusionsschweißen von Siliziumcarbid (1981)
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 12 (1981), S. 227-229 
    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: Diffusion Bonding of Silicon CarbidesSilicon carbide is a material that is suitable for high temperature application, especially for heat exchangers at high temperatures.Besides the problem of producing large components out of ceramics a technique for joining silicon carbide has to be developed. At high temperatures the joint has to be gastight und sufficient strength must be guaranteed. Diffusion bonding proved to be a good technique. The temperatures necessary for diffusion bonding are around 1200 °C, inert atmosphere or vacuum was used. The parameters of the procedures are discussed and correlated to strength, microstructure and permeability for gases.
    Notes: Siliziumcarbid ist ein Werkstoff, der für Hochtemperaturanwendungen, besonders für Hochtemperatur-Wärmetauscher geeignet ist.Neben dem Problem, große Bauteile aus dieser Keramik zu produzieren, muß eine Fügetechnik entwickelt werden. Bei hohen Temperaturen sollen gefügte Teile gasdicht sein und ausreichende Festigkeiten müssen garantiert werden. Diffusionsschweißen hat sich dafür bewährt.Die Temperatur, die für die Diffusionsschweißung in Vakuum oder Schutzgas benötigt worden ist, lag bei 1200 °C. Es werden die Verfahrensparameter in Korrelation zu der Festigkeit des Verbundes, dem Gefüge und der Gasdurchlässigkeit diskutiert.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mawe.19810120702
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  • 8
    Electronic Resource
    Electronic Resource
    Wie sicher sind keramische Kugelköpfe für Hüftendoprothesen (1996)
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 27 (1996), S. 280-286 
    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: How safe are ceramic femoral heads for hip endoprotheses?This is a review of the basic properties, standards, and regulations that are correlated to the application and safety of ceramic femoral heads for hip endoprotheses. The investigation of more than 150 retrieved femoral heads (revisions and autopsies) provides information about the reasons of the failures and was basis for projects to improve ceramic femoral heads.The revision on a hip endoprothesis is mostly caused by aseptic loosening of the stem or the socket. Failures because of materials properties, e.g. fracture of a stem or because of an infection are quite seldom.Because of this investigation it can be concluded that the Biolox femoral head is a safe component in a hip endoprothesis. Based on 20 years clinical experience the in vivo failure rate is less than 0.02% for Biolox femoral heads, 0.01% for heads wite 28mm diameter.
    Notes: Es werden die Gebrauchseigenschaften, Vorschriften und Normen diskutiert, die für die Sicherheit eines keramischen Kugelkopfes bei Hüftendoprothesen relevant sind. Die Auswertung von über 150 Biolox-Explantaten (Revisionen und Autopsien) ergab Hinweise über Versagensursachen und für Maßnahmen zu Verbesserungen.Grund für die Revision einer Hüftendoprothese ist in den meisten Fällen eine aseptische Lockerung des Schaftes oder der Pfanne. Materialversagen, z. B. Schaftbrüche und Infektionen als Ursache für Revisionen haben einen deutlich geringeren Anteil.Analysiert man die Ursachen für Revisionen von künstlichen Hüftgelenken, dann ist der keramische Biolox-Kugelkopf als eine sichere Komponente zu bezeichnen. Basierend auf einer 20jährigen klinischen Erfahrung mit Biolox-Kugelköpfen, liegt für Kugelbrüche in vivo eine Revisionsrate von unter 0,02%, 0,01% für Köpfe mit 28mm Durchmesser.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mawe.19960270606
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  • 9
    Electronic Resource
    Electronic Resource
    Werkstoffkundliche Basis für die Konstruktion mit Ingenieurkeramik (1983)
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 14 (1983), S. 201-207 
    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: Fundamental Properties for the Design with Engineering CeramicsWithin the class of technical ceramics a new group of high quality materials has been developed, called “engineering ceramics”. A definition is given, some of their properties and future applications for mechanical design are pointed out. Comparing to the fundamental properties and definitions known for metallic materials the distinctions and different approach for the design with engineering ceramics are discussed.
    Notes: Unter den technischen keramischen Werkstoffen zeichnet sich eine Gruppe hochwertiger Materialien aus, für die die Bezeichnung „Ingenieurkeramik“ geprägt worden ist. Dieser neue Begriff wird definiert. Eigenschaften und mögliche Anwendungen im Maschinen- und Apparatebau werden vorgestellt. An Hand üblicher, relevanter Begriffe aus der Werkstoffkunde werden die Unterschiede zwischen metallischen Werkstoffen und Ingenieurkeramik und die daraus resultierende andere Vorgehensweise beim konstruktiven Entwurf diskutiert.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mawe.19830140608
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  • 10
    Electronic Resource
    Electronic Resource
    Bruchmechanische Charakterisierung des Ermüdungsverhaltens von SiSiCVorgetragen beim Deutsch-Französischen Kolloquium „Keramische Sonderwerkstoffe“ Lyon, 15.-17. 3. 1983 (1985)
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 16 (1985), S. 94-101 
    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: Fracture Mechanics Characterization of Fatigue in SiSiCThe behaviour of microscopic “natural” cracks and of artificial sharp cracks was investigated on a fracture mechanics base for extruded and slip casted SiSiC. The resulting strength and crack propagation data were used to calculate relations between loading time and probability of fracture and thus provide a base for the practical application of the investigated materials in structures. Examples of calculated life times and probabilities of failure as well as results of experiments performed to check the calculations are discussed.
    Notes: An SiSiC-Keramik wurde sowohl das Verhalten künstlich eingebrachter, makroskopischer Risse als auch das Verhalten der auf die Herstellung und die Bearbeitung zurückzuführenden, „natürlichen“, mikroskopischen Rissen auf bruchmechanischer Grundlage untersucht. Die vorliegenden Ergebnisse zum Festigkeits- und Bruchverhalten und die daraus rechnerisch abgeleiteten und z. T. experimentell überprüften Zusammenhänge zwischen Belastungsdauer und Versagenswahrscheinlichkeit bilden praktisch anwendbare Grundlagen für den Einsatz der untersuchten keramischen Werkstoffe.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mawe.19850160309
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