Temperature “breaks” in Arrhenius plots: A thermodynamic consequence of a phase change

1. When Triton-filled lysosomes from rat liver are incubated for up to 50min at 37°C, pH7.4, in 0.25m-sucrose, no loss of latency of N-acetyl-β-glucosaminidase or p-nitrophenyl phosphatase occurs unless the incubated lysosomes are cooled to approx. 15°C. 2. It is suggested that a phase change takes place in the incubated lysosomal membranes on cooling; it starts at approx. 15°C and probably is not complete at 0°C. 3. Incubation of the lysosomes causes an increased potential for loss of latency of the lysosomal enzymes. This potential is not fully expressed at elevated temperature (e.g. 37°C), but is expressed on cooling. 4. The increase at elevated temperature in potential for loss of latency exhibits biphasic kinetics, with an initial rapid phase followed by a slower phase, which is linear with respect to time. The extra loss of latency resulting from the rapid phase in proportional to the temperature of the incubation. 5. Arrhenius plots of the increase is potential for loss of latency during the slow phase for N-acetyl-β-glucosaminidase and p-nitrophenyl phosphatase exhibit marked deviations from linearity beginning at approx. 15°C. This suggests that the increase in potential for loss of latency is affected by a phase change that occurs around this temperature. 6. Activation energies for the increase in potential for loss of latency at and above 22°C are 53.1±5.4kJ/mol (12.7±1.3kcal/mol) for N-acetyl-β-glucosaminidase and 45.2±7.5kJ/mol (10.8±1.8kcal/mol) for p-nitrophenyl phosphatase. It is postulated that these energies reflect enzymic action, the products of which cause loss of latency to occur on cooling.

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The effect of an aluminum heat-sink layer on the laser-induced amorphization of SiOx/TeGeSn/SiOx phase-change recording films

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100154846 ◽

1989 ◽

Vol 47 ◽

pp. 574-575

Author(s):

Matthew R. Libera ◽

Martin Chen

Keyword(s):

Thin Film ◽

Phase Change ◽

Heat Sink ◽

Multilayer Film ◽

Glassy Phase ◽

Film Structure ◽

Glass Forming ◽

Active Storage ◽

Dielectric Layers ◽

Amorphous States

Phase-change erasable optical storage is based on the ability to switch a micron-sized region of a thin film between the crystalline and amorphous states using a diffraction-limited laser as a heat source. A bit of information can be represented as an amorphous spot on a crystalline background, and the two states can be optically identified by their different reflectivities. In a typical multilayer thin-film structure the active (storage) layer is sandwiched between one or more dielectric layers. The dielectric layers provide physical containment and act as a heat sink. A viable phase-change medium must be able to quench to the glassy phase after melting, and this requires proper tailoring of the thermal properties of the multilayer film. The present research studies one particular multilayer structure and shows the effect of an additional aluminum layer on the glass-forming ability.

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