Thermal stabilization region

On the whole, the correlations that are made concern structure versus phase transition phenomena. In particular we shall concentrate on the identity of mesophases that are formed, the persistence of the mesophase region (thermal stability of the mesophase) and the glass-transition and clearing-point temperatures (Tg and 7 ). But other properties are important also and we shall look at a few correlations between structure and, for example, thermodynamic quantities and dielectric relaxation phenomena. 

Low temperature CO sorption experiments monitored with the IR spectroscopy were used to determine the nature of active (acid) sites present in the Fe-TON zeolites. It is well known that CO is a useful probe molecule for Lewis acid sites. Narrow and well resolved bands appear in the region 2135 - 2150 cm"1. The IR spectra of CO sorbed in amount sufficient to cover all Lewis sites in the Fe-TON of different Si/Fe ratios are presented in Figure 2A. The samples of a high iron content (Si/Fe=27, 36) showed a significantly lower thermal stability. The activation of the NFL form of these Fe-TON... 

Optical fibres composed of plastics are also transparent in the visible spectral region but optical losses reach 102 - 103 dB/km13. Their refractive index varies from 1.35 to 1.6 depending on the kind of polymer used (e.g. polymethymethacrylate PMMA -1.49). The chemical resistance is much worse than that of silica fibres and thermal stability is incomparable. On the other hand, low temperature processes of plastic fibre preparation allow us mix the starting polymer with organic dyes which enables the production of luminescent fibres suitable e.g. for fluorescence-based sensing13. 

At lower temperatures such as those found in the Arctic, the majority of NOy is often present in the form of PAN because of its thermal stability. For example, 50-90% of NOy may exist in the form of PAN in the Arctic spring (Bottenheim et al., 1986 Barrie and Bot-tenheim, 1991 Jaffe, 1993). It is also interesting that, in relatively clean, low-NOx regions at higher tempera-... 

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