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  • 1
    Electronic Resource
    Electronic Resource
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 82 (1999), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The Ag-Bi-O system has been experimentally studied using differential thermal analysis (DTA) and scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX), and thermodynamically optimized. The temperatures of the eutectic, monotectic, and Bi2O3 allotropic transformations have been measured in N2, in air, and in O2 by DTA. There are no ternary phases stable at ambient pressure. Presently measured transformation temperatures have been combined with existing oxygen activity measurements in the metal liquid to optimize thermodynamic parameters describing the liquid phase. The resulting fit is excellent. EDX measurements of the composition in the oxide liquid have a rather low precision but confirm the thermodynamic optimization. However, some uncertainties remain concerning the liquid composition at the eutectic transformation and the shape of the miscibility gap at higher temperatures.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 82 (1999), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Direct coagulation casting is a novel near-net-shape method for forming ceramic green bodies from homogenous high-solids-loaded particle suspensions. It is based on the principle of the in situcoagulation of a powder suspension via a reaction-rate-controlled internal-enzyme(urease)-catalyzed reaction after casting. Low-viscosity (〈3 Pas) suspensions with a high solids loading (〉62 vol%) of SiC, boron, and carbon powder mixtures with a high surface area (〉7-10 m2/g) have been prepared at pH = 10. Salt ions (up to 1-2 mol/L) are created by the urease-catalyzed decomposition of urea, to destabilize the suspensions. The coagulation kinetics and the strength of the wet green bodies have been investigated. The reaction rate is strongly dependent on the temperature (in the range of 5°-30°C) and the enzyme concentration (for the range of 4-16 units/g SiC) and is independent of the substrate (urea) concentration for urea concentrations of 〈2 wt%, based on the powder content. The resulting green bodies show no shrinkage during coagulation and 1%-2% linear shrinkage during drying. The compressive strengths of the wet green bodies are as high as 60 kPa and increase as the coagulation time increases. The wet green strength of the coagulated suspensions scales with the solids content, according to a power law with an exponent of 11, in the range of 56-61 vol% solids content. The possibilities of fabricating high-solids-containing complex SiC green and sintered components with homogenous microstructures and high sintered densities are demonstrated.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 82 (1999), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A water-based route for processing ß-Si3N4 from alpha-Si3N4, Al2O3, and Y2O3 powder mixtures was established. The surface charges and isoelectric points of the three different powders were investigated within the pH range from pH 3 to pH 12. Citric acid diammonium salt was found to be an effective deflocculant for shifting the isoelectric points to pH 3.5 for Al2O3 and to pH 6 for Y2O3. Aluminum hydroxide (Al(OH)3) showed strong interaction with the Si3N4 powder, shifting the isoelectric point from pH 7 to pH 5.5. Low-viscosity, high-solids-loading suspensions (60-63 vol%) thus were possible at pH 9.7. The preparation of homogeneous and stable suspensions with a solids content of ≤61 vol% and a viscosity 〈1 Pa·s was limited to a pH regime between pH 9 and pH 10.5 because of the high solubility of yttria. The homogeneous suspensions were easily solidified by direct coagulation casting (DCC), using the urease-catalyzed decomposition of urea at pH 9 to pH 10, by forming salt. No shrinkage cracking, sedimentation, or phase separation was observed during coagulation or drying. The green-density distribution was homogeneous throughout all bodies, even for complex geometries.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 82 (1999), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The phase relations in the silver-strontium-copper-oxygen (Ag-Sr-Cu-O) and silver-calcium-copper-oxygen (Ag-Ca-Cu-O) systems were studied in oxygen, air, and nitrogen environments, using differential thermal analysis and energy-dispersive X-ray spectrometry. The presence of silver reduces the melting temperature of the oxide liquid to a monotectic in the strontium- and calcium-containing systems by 62 and 82 K, respectively (to 1222 and 1244 K, respectively) in oxygen. The oxide liquid dissolves silver (up to a metallic ratio of 0.17) in the Ag-Sr-Cu-O system in oxygen at a temperature slightly higher than that required for monotectic reaction. In the Ag-Ca-Cu-O system, the silver content has been measured to be 0.29 (metallic ratio). The oxide systems have been optimized using the experimental data from monotectics and those from lower-order systems that have been published previously. This work is part of a project to evaluate the phase relations within the silver-bismuth-strontium-calcium-copper-oxygen (Ag-Bi-Sr-Ca-Cu-O) system and, in particular, to focus on the influence of silver on the phase equilibria around the superconducting phases during partial-melt processing.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 32 (1999), S. 833-836 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A complex high-temperature furnace has been produced from presintered α-Al2O3 precompacts. The furnace is designed for the Mar345 imaging-plate detector system. Up to now, the design complexity of ceramic parts has been limited by the difficulty of machining hard ceramic materials or by the moulds used in hot-pressing and casting. However, the machining of soft presintered ceramic materials enables the realisation of much more demanding designs, provided that the final sintering shrinkage of the ceramic is homogeneous and predictable. The design of the furnace and its realisation and application in an X-ray diffraction study with synchrotron radiation are presented.
    Type of Medium: Electronic Resource
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  • 6
    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
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 169-170 (June 1999), p. 197-200 
    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
    Type of Medium: Electronic Resource
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  • 8
    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
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Monatsschrift Kinderheilkunde 147 (1999), S. 921-923 
    ISSN: 1433-0474
    Keywords: Schlüsselwörter Aseptische Gonarthritis ; Synovitis ; Kniegelenksonographie ; Agammaglobulinämie ; Mykoplasmeninfektion ; Key words Sterile gonarthritis ; Synovitis ; Ultrasonography of the knee ; Agammaglobulinemia ; Mycoplasma infection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary A non-traumatic and sterile effusion of the knee joint was the presenting symptom of agammaglobulinemia in a five year old boy. The patient had experienced recurrent infections, but these had been localized and responded to antibiotics so that the disease had not been diagnosed before. Synovitis of the knee was demonstrated by ultrasonography, while HRCT of the lungs showed thickening and dilatation of bronchial walls. Complete recovery of gonarthritis was achieved following intravenous gamma globulin substitution. Discussion: Agammaglobulinemia has to be considered in the presence of an atraumatic and sterile monarthritis of the knee. Ultrasonography is a valuable diagnostic tool in demonstrating synovitis.
    Notes: Zusammenfassung Ein fünfjähriger Junge entwickelte einen einseitigen nicht traumatischen, aseptischen Kniegelenkerguß, der sonographisch eine ausgeprägte Synovialishyperplasie zeigte. Die weitere Diagnostik erbrachte eine Agammaglobulinämie sowie Bronchiektasen. Eine vollständige und bleibende Remission der Kniegelenkbeschwerden wurde nach i.v. Immunglobulinsubstitution erreicht. Diskussion: Bei einer aseptischen Arthritis sollte auch an einen Immunglobulinmangel gedacht werden. Die Synovitis kann sonographisch gut dargestellt werden.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Der Orthopäde 28 (1999), S. 579-584 
    ISSN: 1433-0431
    Keywords: Key words Lumbar microdiscectomy • Failed back syndrome • Lumbar disc surgery • Percutaneous discectomy • Laserdiscectomy ; Schlüsselwörter Bandscheibenvorfall • Mikrochirurgische Technik • Diskotomie • Operationsmikroskop • Postdiskotomiesyndrom • Perkutane Diskotomie • Laserdiskotomie
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Für die Entscheidung, ob ein lumbaler Bandscheibenvorfall konservativ oder operativ behandelt werden soll, ist allein der klinisch/neurologische Befund maßgebend. Die bildgebenden Verfahren sind zweitrangig. Bei gegebener Indikation stehen heute zahlreiche perkutane endoskopische und offene mikrochirurgische Verfahren zur Verfügung. Die Auswahl der geeigneten Methode hängt von der pathologisch/anatomischen Situation des dislozierten Bandscheibengewebes ab. Bei geschlossenem Bandscheibenring sind noch intradiskale perkutane Verfahren wie perkutane Nukleotomie und Laserdekompression möglich. Die Ergebnisse haben in kontrollierten prospektiv randomisierten Studien enttäuscht. Die zwar effektive, jedoch durch Nebenwirkungen und Komplikationen behaftete Chemonukleolyse bleibt zur Zeit als einziges intradiskales Verfahren übrig. Der endoskopische transforaminale oder interlaminäre Zugang zum lumbalen Bandscheibenvorfall befindet sich noch im Experimentierstadium. Kontrollierte Studien fehlen. Wenn offen operiert wird, besteht ein Trend zum mikrochirurgischen Eingriff. Voraussetzung ist eine klare Indikation mit entsprechendem technischem Umfeld und Training zur Durchführung der gewählten Methode.
    Notes: Summary The decision about operative or non-operative treatment of herniated lumbar discs has to be based on the results of clinical and neurological examination. Results of imaging techniques as CT or MRI are secondary. Various percutaneous endoscopic or open techniques have been described. The most appropriate technique is determined by the anatomical situation of the dislocated lumbar disc tissue. Intradiscal percutaneous therapies such as percutaneous nucleotomy and laser decompression are possible, but they revealed poor results in prospective randomized and controlled studies. Chemonucleolysis remains as an effective intradiscal technique at the time, but is afflicted with side effects and complications. Endoscopic transforaminal or interlaminary techniques are still experimental. Whenever open surgery is necessary, microsurgical techniques are preferred. If a certain technique is to be applied, there has to be the correct indication, technical support for and experience in using the choosen method.
    Type of Medium: Electronic Resource
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