Temperature dependence texture

However, temperature dependence of the twist (the pitch was determined from fingerprint textures) follows Eq. (1) and in both cases gives positive... 

The solubility of lactose as a function of temperature is summarized in Figure 2.5. The solubility of a-lactose is more temperature dependent than that of p-lactose and the solubility curves intersect at 93.5°C. A solution at 60°C contains approximately 59 g lactose per 100 g water. Suppose that a 50% solution of lactose ( 30g /J- and 20 g a-) at 60°C is cooled to 15°C. At this temperature, the solution can contain only 7 g a-lactose or a total of 18.2 g per 100 g water at equilibrium. Therefore, lactose will crystallize very slowly out of solution as irregularly sized crystals which may give rise to a sandy, gritty texture. 

Temperature of the sol-gel processing. Only in cases of the xerogels 40, 73 and 74 has a systematic study demonstrated how much the texture is temperature-dependent. From data in Table 4, an increase in the temperature of the perforation of the gel leads to a decrease in microporosity, an increase in mesoporosity and an increase in specific surface area155. It also appears that the texture of the material is not directly correlated to the degree of polycondensation (see Table 3)151,152. The same effect was also found for the xerogel P(C6H4SiOi.5)3 (30 m2g-x at 20 °C and 340 m2g 1 at 60 °C)109. 

Keep in mind, however, that the types of metamorphic rocks formed under the application of pressure and temperature depend on the mineral composition and texture of the parent, or original, rocks, as well as the amount of pressure and the degree of temperature to which the rocks are subjected, hi general, as the pressure and temperature increase so does the texture, or grain size, of the rocks formed. 

There is also an excellent relation between the microstructure of mesophase and the temperature dependence of AHj/2- For Taiheiyo coal (no anisotropic texture was observed over the temperature range from 400 to 600 K), the temperature at which the value of AHj/2 shows its minimum (AHj/2, min) lower than that for materials that exhibit a fine mosaic mesophase. The values of AHj/2 for materials that exhibit a coarse mosaic or fibrous mesophase stay small over a wide temperature range (see Table II and Figure 3). 

Several fundamental studies have shown the importance of monomer sequence distribution on mesophase behavior (26). Simply changing the direction of ester linkages in a chain affects the transition temperatures, the range of the mesophase stability and, in some cases, even the mesophase texture (2Z). Polyester chains are susceptible to transesterification, which raises the question of which sequence structure is actually responsible for the properties observed for a given polymer. A recent study of aromatic LC polymers by neutron scattering indicates that transesterification occurs in the mesophase at rates twice that in poly(ethylene terephthalate) (28). Such behavior has also been observed to occur in other aromatic polyesters where rapid sequence redistribution was detected by nmr, see for example, the chapters by Jin and Economy et al. The temperature dependence of this effect has not been fully explored, and it may not be as pronounced in those polymers which exhibit mesophase behavior at lower temperatures, for example, those with aliphatic spacers. 

In the case of Ce(>2, there is general agreement that the oxidation step (reaction 1) is a fast and exothermic process. At room temperature this reaction proceeds rapidly on the surface and with an appreciable rate in the bulk. In fact, the rate of re-oxidation at room temperature depends also on the nature of the phase formed in the reduction. As long as non-stoichiometric Ce02 x are formed during the reduction, the subsequent re-oxidation proceeds even at room temperature, irrespectively of the initial texture of the CeC>2. Both a low-surface-area (5 m2 g-1) and a high-surface area (115 m2 g 1 Ce02,... 

Helpful tools for this structurization of liquid crystal research were temperature dependent X-ray investigations [36] of natural and synthetic lipids, and the discovery that mesophases may be identified by their different textures appearing in the microscope using crossed polarizers [37]. In the decade starting in about 1957 systematic screening of the concentration and temperature dependency of the major lyotropic mesophases was done and models of the molecular arrangement in the different phases were developed [38-45] (e.g., the so-called middle or neat phases [38], the cholesteric phase of polypeptides and nucleopep-tides [44]). 

Fig. 34. Left Temperature dependence of the correlation functions Gj and G as derived from the orientational dependence of the muon spin depolarization rate of a strongly textured Dy sample in the paramagnetic regime. From Barsov et al. (1986c). Right Temperature dependence of the relaxation rate A in single-crystalline Dy...

For (lb), having the long flexible spacer of six methylene units a normal nematic phase is observed displaying the typical vi/ell known nematic textures under the polarizing microscope. Marbled textures as well as Schlieren textures can be seen, and they exhibit the same types of defects as ordinary l.-lc s. Conoscopic observations clearly prove the optically uniaxial positive character. The absolute value of the birefringence An as well as the temperature dependence of An correspond to chemically similar l.-lc s ... 

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