X-ray diffraction patterns characteristics

After the war, Bailey returned to studies on muscle, and announced in 1946 the isolation from vertebrate muscle of tropomyosin B, a new myofibrillar protein with unusual properties. This achievement and the later discovery of the family of tropomyosins A are Bailey s most important contributions to the muscle field. The latter protein was shown to be responsible for the paramyosin X-ray diffraction pattern characteristic of molluscan adductor muscles and opened up a new field of interest. The tropomyosins possess a number of remarkable properties which are just those which we would have expected to excite his interest—one cannot help feeling that these proteins were almost custom-built for him. Their function is still something of a mystery but the... 

Besides the x-ray diffraction patterns characteristic of the alpha- and beta-type proteins, there is a third kind that of collagen, the protein of tendon and skin. On the primary level, collagen is characterized by a high proportion of proline and hydroxy proline residues, and by frequent repetitions of the sequence Gly.Pro.Hypro. The pyrrolidine ring of proline and hydroxyproline can affect... 

Crystalline hydrous zirconia has been prepared (115) by refluxing slurries of hydrous zirconia or zirconium oxychloride solutions adjusted to pH values between 1 and 2.5 by addition of ammonia. Final products have an X-ray diffraction pattern characteristic of monoclinic zirconia. Cubic zirconia free of monoclinic zirconia was prepared by heating amorphous hydrous zirconia in the presence of aqueous sodium or potassium hydroxide. Cubic hydrous zirconia was stable to 650°C whereupon it reverted to the monoclinic form. 

The effect of the pH upon the formation of o.33[Cu-Cr-Cl]3R is similar. The best crystallized phase is obtained at the lowest pH value of 5.5. Below this pH, an additional unidentified phase appears. It must be noticed that, in some cases, the pH does not have a direct observable effect on the diffraction pattern. The typical example comes from the q 33[Ni-Cr-Cl] phase. ITiis phase displays the same powder X-ray diffraction patterns characteristic of a quasi-amorphous material, whatever the pH of precipitation from 5.5 to 11.5. However, under hydrothermal treatment, the only phase that crystallizes is the LDH prepared at pH = 11.5. 

Polymers can be divided into two groups morphologically amorphous polymers and crystalline polymers. Amorphous polymers lack sufficient regularity in packing of the chains to produce the sharp x-ray diffraction pattern characteristic of highly crystalline polymers. The term crystalline polymer is actually a misnomer since no polymer is 100% crystalline, containing both crystalline domains and amorphous domains. Therefore, a more correct yet seldom used designation is semicrystalline polymer. 

Figure 10 Powder X-ray diffraction pattern characteristic of AMF, MF-TAGs, and MF-... 

According to Biscoe and Warren (40,41), the turbostratic structure (unordered layers), first found in carbon black (amorphous graphite), consists of roughly parallel 6-ring layers that are piled up at translational and rotational random about the layer normal. The material called tBN shows the halo X-ray diffraction pattern characteristic of this turbostratic structure (Fig. 4). It has a broad diffraction peak around 2 0 = 25° to the distance between the layers (-333 pm) (Fig. 3) (42). 

Idistribution functions can be measured experimentally using X-ray diffraction. The regular arrangement of the atoms in a crystal gives the characteristic X-ray diffraction pattern with bright, sharp spots. For liquids, the diffraction pattern has regions of high and low intensity but no sharp spots. The X-ray diffraction pattern can be analysed to calculate an experimental distribution function, which can then be compared with that obtained from the simulation. 

The index of refraction of allophane ranges from below 1.470 to over 1.510, with a modal value about 1.485. The lack of characteristic lines given by crystals in x-ray diffraction patterns and the gradual loss of water during heating confirm the amorphous character of allophane. Allophane has been found most abundantly in soils and altered volcanic ash (101,164,165). It usually occurs in spherical form but has also been observed in fibers. 

Mica [12001 -26-2]—Cl Pigment White 20, Cl No. 77019. A white powder obtained from the naturally occurring mineral muscovite mica, consisting predominantly of a potassium aluminum siHcate, [1327-44-2] H2KAl2(Si0 2- Mica may be identified and semiquantitatively determined by its characteristic x-ray diffraction pattern and by its optical properties. 

Many polymers show partial crystallinity. This is apparent from the study of X-ray diffraction patterns, which for polymers generally show both the sharp features associated with crystalline regions as well as less well-defined features which are characteristic of disordered substances with liquid-like arrangements of molecules. The co-existence of crystalline and amorphous regions is typical of the behaviour of crystalline polymers. 

Zeolites. In heterogeneous catalysis porosity is nearly always of essential importance. In most cases porous materials are synthesized using the above de.scribed sol-gel techniques resulting in so-called amorphous catalysts. Porosity is introduced in the agglomeration process in which the sol is transformed into a gel. From X-ray Diffraction patterns it is clear that the material shows only weak broad lines, characteristic of non-crystalline materials. Silica and alumina are typical examples. Zeolites are an exception they are crystalline materials but nevertheless exhibit high (micro) porosity. Zeolites belong to the class of molecular sieves, which are porous solids with pores of molecular dimensions, i.e., typically the pore diameter ranges from 0.3 to 10 nm. Examples of molecular sieves are carbons, oxides and zeolites. 

TUD-1 is an amorphous material. Unlike crystalhne stractnres, it has no characteristic x-ray diffraction pattern. Figure 41.1 illustrates the pore diameter of TUD-1 in comparison to some major molecular sieves - ZSM-5, Zeohte Y, and MCM-41. It is important to note that the pore diameter of TUD-1 can be varied from about 40A to 250 A. 

Typical X-ray diffraction patterns of three different carbon powder samples are shown in Fig. 3. Two 00/ and two hkO diffraction peaks can be distinguished in the patterns of samples produced at 800°C and 1000°C. The 002 (26 26.9°) and 004 (26 54.9°) peaks correspond to the parallel graphene layers. The 100 (26 43°) and 110 (26 77.8°) diffraction peaks are characteristics of the 2D in-plane symmetry along the graphene layers. Based on its XRD pattern, the powder synthesized at 500°C is not graphitized, which is in agreement with Raman analysis. This low temperature sample also contains traces of iron chlorides. 

Gorevic, P. D., Castano, E. M., Sarma, R., and Frangione, B. (1987). Ten to fourteen residue peptides of Alzheimer s disease protein are sufficient for amyloid fibril formation and its characteristic x-ray diffraction pattern. Biochem. Biophys. Res. Commun. 147, 854-862. 

These crystals of reduced horse haemoglobin had some interesting properties which had not been observed previously. Normally when crystals of reduced haemoglobin are exposed to air they break up and most of their X-ray diffraction pattern disappears indicating that the crystals arc disordered. However when these crystals were left to become oxygenated or were slowly oxidised characteristic, well ordered lattice changes appeared. The unit cell dimensions were unchanged except for a... 

Figure 11 X-ray diffraction pattern of a precipitate that has been calcined at 850°C for 20 min under oxygen and quenched, (a) Starting from a precipitate of acetates (35). Peaks corresponding to the 123 phase can be seen mixed with peaks characteristic of BaCOs. (b) Starting from hydroxides (54). The pure tetragonal 123 phase is observed.

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