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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Bioprocess and biosystems engineering 10 (1994), S. 1-3 
    ISSN: 1432-0797
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Fluidized-bed bioreactors (FBRs) with immobilized cells have been used successfully at Oak Ridge National Laboratory and at the Autonomous University of Barcelona for several applications, including high-productivity yields of ethanol. During the development of these processes, experimental results have revealed differences between three-phase fluidized biocatalyst systems and those systems typically used for hydrodynamic studies. These differences appear to be related to the physical properties (density, viscosity, surface tension) of the phases and, in particular, the low density of the solid particles. Parameters were calculated from these physical properties following the approach of Baker for two-phase flow. A map of these parameters was proposed previously and separated regions of satisfactory and unsatisfactory fluidization of a three-phase immobilized-yeast FBR fluidized with air. This same map was used for an FBR with immobilized Zymomonas mobilis that was liquid fluidized. The stability regions on the map corresponded to the two different experimental operating systems. This indicates the possible general applicability of this approach to biological FBRs.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 319-332 
    ISSN: 1572-8943
    Keywords: freeze-drying ; glass transitions in frozen systems ; heat capacity calibration ; Lissajous figures ; sucrose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Temperature modulated DSC (TMDSC) at low temperatures requires attention to the selection of experimental parameters that are within the capability of the instrumentation as well as special care in calibration of heat capacity measurement when high precision is required. Data are presented to facilitate selection of appropriate modulation periods and amplitudes at low temperature when using a mechanical cooling accessory. The standard error of the mean heat capacity measurement for a sapphire standard increased with decreasing temperature, decreasing period, and increasing pan mass. For ice in hermetically sealed pans, the standard error of the mean heat capacity measurement was larger than for sapphire and did not follow a predictable trend with changes in temperature and period of modulation. This was attributed to changes in sample geometry between successive measurements due to melting and resolidification. A simple one-point temperature calibration by TMDSC may be unsuitable for precise measurement of heat capacity because of the random error caused by sample placement and the systematic error caused by cell asymmetry, temperature dependence of the calibration constant, and different sample thermal conductivities. An alternative calibration procedure using standard DSC and either a linear or second order fit of the calibration constant over the temperature range of interest is proposed.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of thermal analysis and calorimetry 54 (1998), S. 659-672 
    ISSN: 1572-8943
    Keywords: frozen sucrose solutions ; TMDSC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract This study compares measurements of the collapse temperature of sucrose solutions by freeze drying microscopy with features of TMDSC curves both in the scanning and quasi-isothermal modes. The objective was to determine which feature of the TMDSC curve is predictive of collapse and to provide additional evidence for recent interpretations of the physical significance of the low temperature transitions for sucrose solutions. Interpretations based on the heat capacity signal and the kinetic heat flow using TMDSC are consistent with previous reports based on total heat flow measurement, where the lower temperature transition is the glass transition and the higher temperature transition is associated with the onset of ice melting. Quasi-isothermal experiments further support these conclusions, since additional crystallization of ice is observed only in the region of the lower temperature transition. Collapse of sucrose solutions during freeze-drying begins at the approximate midpoint between the end of the glass transition region and the onset of ice melting.
    Type of Medium: Electronic Resource
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