diffraction
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Practical methods in electron microscopy ; Vol. 12
XVI, 287 s. : il. ; 24 cm
Crystalline order of molded and then bi-axially stretched foils prepared from atactic PVC resin is investigated by means of wide-angle neutron diffraction (WAND). The observed high-resolution WAND patterns of all samples are dominated by a sharp maximum corresponding to the inter-planar distance 0.52 nm. Two weaker maxima are also resolved at 0.62 and 0.78 nm. Intensities of the peaks vary with deformation ratios of the samples and their diffraction position. Average size of the coherently scattering domains is estimated as approximately 4-8 nm. Based on the experimental data, a novel model of crystalline order of atactic PVC is proposed.
A considerable number of fatal intoxications have recently been connected with the growing popularity of new psychoactive substances (NPS). Therefore, there is a significant demand for the development of fast and facile field detection methods for NPS. These substances are often sold as blends (with inorganic or organic cutting agents), which may further complicate detection. X-Ray powder diffraction (XRPD) was evaluated as a suitable and easily employable analytical method for the identification of NPS. XRPD has been successfully used for the differentiation of eight synthetic cathinones with a similar molecular structure. Moreover, this method was also used for the identification of four drugs in authentic street samples. XRPD is a facile non-destructive method that can identify not only NPS in mixtures but also the cutting agents. The small amount of substances needed for the measurement, which can be re-used for other analyses, further enhances the versatility of this method.
The small bacterial laccase from the actinobacterium Streptomyces coelicolor which lacks the second of the three domains of the laccases structurally characterized to date was crystallized. This multi-copper phenol oxidase crystallizes in a primitive tetragonal lattice, with unit-cell parameters a = b = 179.8, c = 175.3 A. The crystals belong to either space group P4(1)2(1)2 or P4(3)2(1)2. The self-rotation function shows the presence of a noncrystallographic threefold axis in the structure. Phases will be determined from the anomalous signal of the natively present copper ions.
