X-rays patterns

Amorphous or "plastic" sulfur is obtained by fast cooling of the crystalline form. X-ray studies indicate that amorphous sulfur may have a helical structure with eight atoms per spiral. Crystalline sulfur seems to be made of rings, each containing eight sulfur atoms, which fit together to give a normal X-ray pattern. 

The nickel oxide modification obtained electrochemicaHy in KOH electrolyte contained potassium ion and its nickel oxidation level are higher than that of NiO 5. Conclusions regarding the transitions between the reduced and oxidized products within the two series are that the redox process was not reversible and although the oxidized phases of the P- and the y-nickel hydroxides differ in energy contents, differences in analyses and x-ray patterns are not significant. 

Because of its regularity it would be expected that the polymer would be capable of crystallisation. In practice, however, the X-ray pattern characteristics of crystalline polymer is absent in conventionally fabricated samples. On the other hand films which have been prepared by slow evaporation from solvent or by heating for several days at 180°C do exhibit both haziness and the characteristic X-ray diagram. The amount of crystallisation and the size of the crystallite structures decrease with an increase in the molecular weight of... 

Many studies, primarily via X-ray patterns, have led to the following picture of NC of varying degree of nitration ... 

Just as an example, the X-ray diffraction patterns of compression moulded samples of PVDF, poly(vinylfluoride), and of some VDF-VF copolymers of different compositions are shown in Fig. 17 [90]. The degrees of crystallinity of the copolymer samples (40-50%) are high and analogous to those of the homopolymer samples. This indicates a nearly perfect isomorphism between the VF and VDF monomeric units [90, 96], The diffraction patterns and the crystal structures of the copolymers are similar to those of PVF, which are in turn similar to the X-ray pattern and crystalline structure of the P form of PVDF. On the contrary, the X-ray pattern of a PVDF sample crystallized under the same conditions (Fig. 17 a) is completely different, that is typical of the non-piezoelectric a form [90]. 

The second choice is a simpler solution. According to Sarko and Muggli,66 all 39 observed reflections in the Valonia X-ray pattern are indexable by a two-chain triclinic unit cell with a = 9.41, b =8.15 and c = 10.34 A, a = 90°, 3 = 57.5°, and y = 96.2°. Ramie cellulose, on the other hand, is completely consistent with the two-chain monoclinic unit cell. Also, there are significant differences between their high-resolution solid-state l3C NMR spectra, indicating that Valonia and ramie celluloses, the two most crystalline forms, reflect two distinct families of biosynthesis. On this basis, the Valonia triclinic and the ramie monoclinic forms are classified69 as Ia and Ip, respectively. It has been shown from a systematic analysis of the NMR spectra by these authors, and from electron-dif-... 

In a subsequent study (S9), isotherms of bromine on pyrolytic graphite showed the presence of several phases C4 Br (n = 2 to 5). X-ray studies confirmed these to be stages 2 to 5, respectively. At intermediate concentrations, X-ray patterns showed mixtures of higher and lower stages. The density and configuration of intercalated bromine molecules were believed to be the same in all stages. Other structural types... 

Several methods based on the utilization of x-rays are nsed to study LB fihn structure. Diffractometry and reflectometry are the nsnal ones. Diffractometry is nsed mainly when well-ordered periodic strnctnre is under the investigation and several Bragg reflections are in the x-ray pattern. The position of these reflections is determined by the Bragg eqnation ... 

FIG. 22 X-ray pattern of LB fibn containing 20 layers of wild-type cytochrome P450 see. 

XRD analysis of the solid product showed three main peaks at 28.5 , 47.4 and 56.3 , which indicated that pure crystalline CuCl was formed [3]. Several well-known dispersants polyvinyl pyrrolidone (PVP), sodium hexameta phosphate (SHP), the sodium salt of EDTA (EDTA-Na), sodium dodecyl sulfonate (SDS), and sodium dodecyl benzene sulfonate (SDBS), were introduced to obtain a highly dispersed catalyst. The X-ray patterns obtained with these were basically the same as the patterns obtained with the solids prepared in the other experiments described here. 

Fig. 6 displays the X-ray powder diffraction patterns of rhenium oxide. While the as-prepared sample is amorphous to X-ray, the sample soaked in acetone and dried at 100"C clearly exhibits sharp reflections corresponding to Re03. The large difference between the two X-ray patterns suggests that the processing conditions play a key role in the crystallinity and surface characteristics. As shown in the TGA plot of the as-prepared sample (Fig. 7), the weight loss of about 10% below 100 C results from the loss of water. 

The polymer = 8.19 dlg in hexafluoro-2-propanol, HFIP, solution) in Figs 1 and 2 is prepared on photoirradiation by a 500 W super-high-pressure Hg lamp for several hours and subjected to the measurements without purification. The nmr peaks in Fig. 1 (5 9.36, 8.66 and 8.63, pyrazyl 7.35 and 7.23, phenylene 5.00, 4.93, 4.83 and 4.42, cyclobutane 4.05 and 1.10, ester) correspond precisely to the polymer structure which is predicted from the crystal structure of the monomer. The outstanding sharpness of all the peaks in this spectrum indicates that the photoproduct has few defects in its chemical structure. The X-ray patterns of the monomer and polymer in Fig. 2 show that they are nearly comparable to each other in crystallinity. These results indicate a strictly crystal-lattice controlled process for the four-centre-type photopolymerization of the [l OEt] crystal. 

Obtain a suitable x-ray pattern using a single crystal of the material. 

We also see (Fig. 6) that raising the calcination temperature of rare earth modified silica-aluminas from 500 to 600°C, may slightly sinter the rare earth oxide. Although the x-ray pattern... 

Most DNA, natural and synthetic, can adopt the B-form as defined by its characteristic X-ray pattern [3]. There are few a species of synthetic DNA, namely poly(dA) poly(dT), poly(dI) poly(dC), poly(dA-dI) poly(dC-dT) and poly(dI-dC)-poly(dI-dC), which have a B-form that significantly differs from that of the other complementary deoxy polymers due to their different intramolecular packing arrangements and slightly changed value for the rise per residue. The helix parameters are presented in Table 1. The linear sequen-... 

Kitian, H. G. and Pieper, T. Packing of Chain Segments, A Method for Describing X-Ray Patterns of Crystalline, Liquid Crystalline and Non-Crystalline Polymers. Vol. 108, pp, 49-90. 

Inulin crystallizes in the form of doubly refracting sphero-crystals, the crystalline structure of which is indicated by x-ray patterns.6,4 In aqueous solution inulin has a specific rotation [ajo20 = — 39 to — 40° referred to the anhydrous substance. 

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