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  • 1
    Electronic Resource
    Electronic Resource
    High- and low-temperature limits to growth of tomato cells (1994)
    Springer
    Planta 195 (1994), S. 1-9 
    Details
    ISSN: 1432-2048
    Keywords: Calorimetry ; Chilling ; Heat-stress injury ; Lycopersicon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The temperature dependence of the metabolic rates of cultured tomato cells (Lycopersicon esculentum Mill.) has been studied by differential scanning calorimetry as a continuous function over the range from near 0 to above 45°C. Metabolic rates increase exponentially with temperature over the permissive range for growth (approx. 10–30°C). Outside this range irreversible loss of metabolic activity occurs. The rate of activity loss is time and temperature dependent, increasing as the exposure temperature diverges from the permissive range and increasing with time at any nonpermissive temperature. Metabolic heat rates obtained while scanning down from intermediate (25°C) to low temperature (0°C) yielded Arrhenius plots with pronounced downward curvature below about 12°C. The increase in apparent activation energy below 12°C is a function of the scan rate, showing its time dependency. This time dependency caused by inactivation confounds many estimates of apparent activation energy. Scanning up to high temperature shows that activity loss at high temperature is also time and temperature dependent. No first-order phase transitions associated with the changes in metabolism were detected at either low or high temperatures. Studies with lamellar lipid preparations added to cells show that temperature-induced transitions of lipids at levels equivalent to 4% of the lipid content of the cells were detectable. Cells with altered lipid composition showed altered temperature dependence of inactivation. High pressures (in the range from 10 to 14 MPa) shift the high temperature threshold and the rate of metabolic activity loss, supporting a postulate that higher-order transitions may be associated with inactivation of metabolism. Higher-order transitions of lipids or first-order transitions encompassing only a small fraction of total lipid remain among several viable postulates to explain temperature-dependent loss in activity. Alternative postulates are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00206284
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  • 2
    Electronic Resource
    Electronic Resource
    n-hexane as a model for compressed simple liquids (1994)
    Springer
    International journal of thermophysics 15 (1994), S. 415-441 
    Details
    ISSN: 1572-9567
    Keywords: n-hexane ; isobaric thermal expansivities ; pressure-controlled scanning calorimetry ; saturated vapor pressure ; specific volume ; heat capacityisothermal compressibility ; thermal coefficient of pressure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Isobaric thermal expansivities, αp, ofn-hexane have been measured by pressure-controlled scanning calorimetry from just above the saturation vapor pressure to 40 MPa at temperatures from 303 to 453 K and to 300 MPa at 503 K. These new data are combined with literature data to obtain a correlation equation for αp valid from 240 to 503 K at pressures up to 700 MPa. Correlation equations are developed for the saturated vapor pressure, specific volume, and isobaric heat capacity of liquid n-hexane from 240 to 503 K. Calculated volumes, isobaric and isochoric specific heat capacities. isothermal compressibilities, and thermal coefficients of pressure are presented for the entire range of pressure and temperature. The pressure-temperature behavior of these quantities is discussed as a model behavior for simple liquids without strong intermolecular interactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01563706
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