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  • 1995-1999  (2)
  • 1970-1974  (1)
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  • 1
    Digitale Medien
    Digitale Medien
    Doubly entrapped baker's yeast survives during the long-term stereoselective reduction of ethyl 3-oxobutanoate in an organic solvent (1998)
    Springer
    Applied microbiology and biotechnology 49 (1998), S. 377-381 
    Details
    ISSN: 1432-0614
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract To attain long-term bioreaction in organic solvents with living microorganisms, we tried to protect the microorganisms from the toxicity of the solvent by immobilization. In this study, baker's yeast, which is not tolerant to organic solvents such as isooctane, was selected as a model microorganism and the immobilized living yeast cells were examined for activity in the steroselective reduction of ethyl 3-oxobutanoate to ethyl (S)-3-hydroxybutanoate in isooctane; an activity that correlated well with the viability of the yeast cells. It was found that double entrapment, that is, further entrapment of calcium-alginate-gel-entrapped cells with a urethane prepolymer, made it possible for the yeast to remain viable in isooctane, although other conventional immobilization methods, such as single entrapment using polysaccharide or synthetic resin prepolymers, were insufficient for its protection. Furthermore, doubly entrapped living yeast cells could carry out the stereoselective reduction in isooctane repeatedly for a long period (more than 1200 h) with occasional cultivation. Thus, double entrapment enabled a microorganism sensitive to organic solvents to survive over long-term bioreaction in an organic solvent.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002530051185
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  • 2
    Digitale Medien
    Digitale Medien
    Theoretical approach to the fracture of two-phase glass-crystal composites (1972)
    Springer
    Journal of materials science 7 (1972), S. 973-982 
    Details
    ISSN: 1573-4803
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract This paper proposes a fracture theory for two-phase glass-crystal composites. It is hypothesized that the fracture mechanisms of such solids consist of the processes of crack nucleation and of crack propagation round the dispersed particles. At lower volume fractions of dispersed phase, macroscopic fracture will occur as a result of the growth of the micro-cracks originating in the vicinity of the pre-existing structural imperfections through a heterogeneous nucleation process; in this case, strength decreases with the proportion of the dispersed phase. At higher volume fractions where further crack propagation is prohibited by the hard crystalline particles, the process of crack propagation round the dispersed particles may be responsible for the macroscopic fracture of the composite; in this case, strength is an increasing function of the volume fraction. Expressions are formulated for mechanical strength of the glass-crystal composites, based upon the nucleation theory and Griffith's criterion. The published data on the strength of glass-alumina composites are used for the verification of the theory. The proposed theory explains well the strength behaviour of glass-alumina composites, and in particular, the dependence of the strength reduction on particle size at lower volume fractions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00550059
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  • 3
    Digitale Medien
    Digitale Medien
    Slip casting of sialon for pressureless sintering (1998)
    Springer
    Journal of materials science 33 (1998), S. 2889-2892 
    Details
    ISSN: 1573-4803
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The properties of aqueous slips of sialon were studied. Ammonium polyacrylate was used as a deflocculant. It was shown that the apparent viscosity for slips with solid content 40 vol % was low and the slip resulting from this is almost Newtonian. This slip proved sufficiently fluid for casting. However, the apparent viscosity for slips with solid content 45 vol % increased significantly. The slips resulting from this exhibited dilatant flow and were difficult to cast. The viscosity, fluidity, and pH of the slips were studied and tiles were cast and fired in nitrogen at 1740 °C for 3 h to a bulk density of 3.20 g cm−3.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1017502323451
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