Based on Electron Diffraction

D Molecule Representation of Structures Based on Electron Diffraction Code (3D MoRSE Code)... 

The above remark about resolution also applies to electron diffraction, and in fact, resolution is one of the most serious limitations in structure determination based on electron diffraction from powder samples. The poor... 

Table 4 presents molecular dimension parameters of 1,2,3-triazole and 2-methyl-4-trinitromethyl-2//-1,2,3-triazole based on electron diffraction (ED) data alone, joint analysis of electron diffraction and microwave spectral data (ED-MW), and ab initio calculations. The corresponding molecular dimensions of 1,2,3-triazoles in the crystalline state obtained by x-ray diffraction (XD) are the average values based on <85ACS(A)259>. Figure 5 shows the bond distances and angles of the crystal structure of 2-phenyl-4-chloro-1,2,3-triazole <84ACS(A)497>. As examples of 4,5-unsubstituted H-... 

This paper is a review of x-ray diffraction work in the authors laboratory to refine the structures of cellulose I and II, and a- and B-chitin, concentrating on the methods used to select between alternate models. Cellulose I is shown to consist of an array of parallel chains, and this conclusion is supported by a separate refinement based on electron diffraction data. In the case of cellulose II, both parallel and antiparallel chain... 

D-molecule representation of structures based on electron diffraction 3D-MoRSE descriptors... 

D-MoRSE descriptors ( 3D-M0lecule Representation of Structures based on Electron diffraction, MoRSE descriptors)... 

The STM results confirmed the LEED ones and permitted to clarify some structural elements that the analysis based on electron diffraction could not solve [27]. The STM studies were performed on samples treated in the same way (i.e. ion bombardment and annealing) as the (111) surface. Also here, the STM data were preceded and complemented by parallel AES, LEIS and LEED studies carried out in the same vacuum chamber. Evidence for Sn depletion due to preferential sputtering was reported and after the annealing at 1000 K the Pt/Sn ratio was found to be close to the bulk value by AES. 

Many years later, it was found that this characteristic of the descriptor could be used for the correlation of biological activity and three-dimensional structure of molecules. The activity of a compound also depends on the distances between atoms (such as H-bond donors or acceptors) in the molecular structure [91]. Adaptation of the RBF function to biological activity led to the so-called 3D-MoRSE code (3D-Molecule Representation of Structures based on Electron diffraction) [92]. The method of RBF calculation can be simplified in order to derive a descriptor that includes significant information and that can be calculated rapidly ... 

Gasteiger et al. returned to the initial I s) curve and maintained the explicit form of the curve [36]. For A they substituted various physicochemical properties such as atomic mass, partial atomic charges, and atomic polarizability. To obtain uniform length descriptors, the intensity distribution I s) is made discrete, calculating its value at a sequence of evenly distributed values of, for example, 32 or 64 values in the range of 0 - 3lA. The resolution of the molecule representation increases with higher number of values. The resulting descriptor is the 3D MoRSE (Molecular Representation of Structures based on Electron diffraction) Code. 

RDFs have certain characteristics in common with the 3D Molecular Representation of Strnctnres Based on Electron Diffraction (MoRSE) code. In fact, the theory of RDF is related to the theoretical basis of 3D MoRSE functions. In 1937, Degard nsed the exponential term in the RDE to account for the experimental angular limitations in electron diffraction experiments [2]. 

Later studies by Sugiyama et were based on electron diffraction and were directed at addressing questions concerning the nature of the differences between the Iq, and I forms of cellulose. In a landmark study, electron diffraction patterns were recorded from V. macrophysa both in its native state, wherein the Iq, and Ifj forms occur in their natural relative proportions, and after annealing using the process first reported by Horii and coworkers, which converts the Iq, form into the I form. The native material, which is predominantly the Iq, form, was shown to produce a complex electron diffraction pattern similar to that which had earlier led Honjo and Watanabe to propose an eight-chain unit cell. In sharp contrast, the annealed sample, which is essentially all of the I form, produced a more simple and symmetric pattern that could be indexed approximately in terms of a two-chain monoclinic unit cell. 

The close relationship between cellulose IV and the native state is also reflected in reports of its observation in the native state of primary cell-wall celluloses. These were the observations based on electron diffraction studies of isolated primary cell-wall celluloses. ... 

For nonstoichiometric UjOs-x. Sato et al. 205) have proposed an out-ofstep model based on electron diffraction observations of the low temperature a-UjOg., phase, according to which the arrangement of hexavalent and pentavalent uranium atoms is altered by the occurrence of an out-of-step structure accompanying the change of composition from UgOg to UgOg., as shown in Fig. 13. 

ANN = artificial neural network CPG = counterpropagation 3D-MoRSE = 3D molecular representation of structures based on electron diffraction FREL = fragment reduced to an environment that is limited. 

In the three-dimensional (3D) approach the 3D structure (see Structure Generators) of a molecule is transformed into a structure code. This is performed by regarding every atom pair in the molecule as a point scatterer and calculating the center symmetric diffraction pattern of the molecule as it would be obtained from an electron diffraction experiment. Based on these equations the 3D molecular representation of structures based on electron diffraction (3D-MoRSE) code has been developed. The 3D-MoRSE code is calculated using the equation... 

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