High Transition-Temperature

The relaxatioa temperature appears to iacrease with increa sing HFP coateat. Relaxatioa iavolves 5—13 of the chaia carboa atoms. Besides a and y relaxations, one other dielectric relaxation was observed below —150° C, which did not vary ia temperature or ia magnitude with comonomer content or copolymer density (55). The a relaxation (also called Glass 1) is a high temperature transition (157°C) andy relaxation (Glass 11) (internal friction maxima) occurs between —5 and 29°C. 

In the paramagnetic regime, the evolution of the EPR line width and g value show the presence of two transitions, observed at 142 and 61 K in the Mo salt, and at 222 and 46 K in the W salt. Based on detailed X-ray diffraction experiments performed on the Mo salt, the high temperature transition has been attributed to a structural second-order phase transition to a triclinic unit cell with apparition of a superstructure with a modulation vector q = (0,1/2, 1/2). Because of a twinning of the crystals at this transition, it has not been possible to determine the microscopic features of the transition, which is probably associated to an ordering of the anions, which are disordered at room temperature, an original feature for such centrosymmetric anions. This superstructure remains present down to the Neel... 

Figure 13.5 Microcalorimetry thermograms (not concentration normalized) showing the destabilizing influence of 0.9% benzyl alcohol (dashed trace) on two high-temperature transitions associated with the Fc domains of an IgGjFc fusion protein. Note that 0.1% phenol exhibits very little influence on the unfolding behavior of the protein in comparison to the control (not containing preservative).

The high-volatile Liddell bituminous coal (Figure 2 (E)) shows little indication of thermally-activated molecular mobility below 500 K. There is some fusion between 500 and 600 K followed by a major fusion transition above 600 K which appears very similar to the high temperature transition of the Amberley coal. This Liddell coal, however, has only 6% liptinite, has a crucible swelling number of 6.5 and exhibits considerable Gieseler fluidity. We therefore attribute this high temperature fusion event to the aromatic-rich macerals of the coal and associate it with the thermoplastic phenomenon. This implies that a stage has been reached in the coalification processes at which aromatic-rich material becomes fusible. 

Nature of High Temperature Transitions of the Aromatic Polyesters.. 227... 

Fig. 23. Heat capacities of two cycloalkanes in the transition regions. The low temperature polymorphs are fully ordered. The high temperature transitions lead to the isotropic melts. The condis crystals exist between the two endotherms (Scanning calorimetry, heating rate 10 K/min, drawn after data of Ref.171>)...

Hussein IA, Williams MC (2004) Melt flow indexer evidence of high-temperature transitions in molten high-density polyethylene. J Appl Polym Sci 91 1309... 

Rn Semiconductor metal transition occurs at 150°K (cooling), at 180°K (heating). The resistivity changes through the transition by a factor of 10. The low-temperature phase is monoclinic. A noncooperative, high temperature transition occurs over the temperature range 110°C < T < 260°C. 

Hicrodilatometer results can also be correlated with a non-pristine coal, Bruceton hvA bituminous (24). As shown in Figure 9. the softening temperature (T,) corresponds to a second minor transition within the high temperature region. Contraction temperature (Tc) occurs at the steepest part of the high temperature transition curve in the IGC. 

Figure 3. Partial scan-rescan experiment on yeast alcohol dehydrogenase at pH 7. Scanning to 57 C results in one transition being observed (bottom). Rescanning the same sample results in the absence of low temperature transition (middle) while the high temperature transition is largely unchanged compared to the scan over the full temperature range (top).

The basic idea of the algorithm to be described here (i.e. temperature accelerated dynamics ) is that by increasing the temperature, the overall rate at which activated processes take place is increased. However, altering the temperature also has the effect of changing the relative rates of these microscopic processes and can even turn on processes that would for all practical purposes not even have taken place at the lower temperature of interest. As a result, it is necessary to correct for the temperature induced bias that is present at the higher temperature. Hence, some of the high-temperature transitions are filtered out so as to restore the hierarchy of low-temperature transitions. 

On the other hand, 4-hydroxybenzoic acid and syringic acid give infusible polymers exhibiting high temperature transitions at 330 and 320 °C, respectively. The polymer obtained from 3,5-dichloro-4-hydroxybenzoic acid exhibits neither a melting point nor a transition below 400 °C. 

The induction time for the initial endothermic bond breaking reaction can be calculated using the high pressure, high temperature transition state theory. Experimental unimolecular gas phase reaction rates under low temperature (<1000K) shock conditions obey the usual Arrhenius law ... 

TABLE 4. High Temperature Transition Temperatures and Melting Point of Rare Earth Metals... 

Grossmann HP, Pechhold WR (1986) The high temperature transition of polyethylene into a condis jhase, described on the basis of the duster-entre y hypothesis (QEH). Colloid and Polymer Sea., 264 415... 

Since BCZY15 behaves approximately as a combination of the two component compositions, the magnitudes of the BaCOs-presence temperature range and high-temperature transition hysteresis are approximately equal to the greater of the two... 

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